#include <bits/stdc++.h>
using namespace std;

class input {

private:

    FILE* fin;
    const int sz = 10000;
    char* buff, c;
    int p;

    char read()
    {
        if (p == sz)
        {
            fread(buff, 1, sz, fin);
            p = 0;
            return buff[p++];
        }
        else
            return buff[p++];
    }

public:
    
    input(const char* name)
    {
        c = '-';
        buff = new char[sz];
        p = sz;
        fin = fopen(name, "r");
    }

    void close()
    {
        fclose(fin);
    }

    void open(const char* name)
    {
        c = '-';
        p = sz;
        fin = fopen(name, "r");
    }

    input& operator >> (int& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;
        int sng = 1;

        if (c == '-')
            sng = -1, c = read();

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        n *= sng;

        return *this;
    }

    input& operator >> (long long& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;
        int sng = 1;

        if (c == '-')
            sng = -1, c = read();

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        n *= sng;

        return *this;
    }

    input& operator >> (char& ch)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        ch = c;

        return *this;
    }

    input& operator >> (string& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = "";

        while (c != ' ' && c != '\n' && c != '\0')
            n += c, c = read();

        return *this;
    }

    input& operator >> (double& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        if (c != '.')
            return *this;

        c = read();

        double p10 = 10;

        while (isdigit(c))
            n = n + double(c - '0') / p10, c = read(), p10 *= 10;

        return *this;
    }

    void getline(string& s)
    {
        s = "";

        c = read();

        while (c == ' ')
            c = read();

        while (c != '\n')
            s += c, c = read();
    }
};
class output {

private:
    FILE* fout;
    const int sz = 10000;
    char* buff;
    int p;

    void write(char ch)
    {
        if (p == sz)
        {
            fwrite(buff, 1, sz, fout);
            p = 0;
            buff[p++] = ch;
        }
        else
            buff[p++] = ch;
    }

public:

    output(const char* name)
    {
        buff = new char[sz];
        p = 0;
        fout = fopen(name, "w");
    }

    ~output()
    {
        fwrite(buff, 1, p, fout);
    }

    output& operator << (int n)
    {
        if (n < 0)
            write('-'), n *= -1;

        if (n == 0)
        {
            write(n + '0');
            return *this;
        }

        if (n / 10 != 0)
            *this << (n / 10);

        write(('0' + (n % 10)));

        return *this;
    }

    output& operator << (long long n)
    {
        if (n < 0)
        {
            write('-');
            n *= -1;
        }

        if (n < 10)
        {
            write(n + '0');
            return *this;
        }

        *this << (n / 10);
        write((n % 10) + '0');

        return *this;
    }

    output& operator << (char c)
    {
        write(c);
        return *this;
    }

    void precision(double n, int x)
    {
        *this << int(n);

        if (!x)
            return;

        write('.');

        n -= int(n);
        n *= 10;

        for (int i = 1; i <= x; i++)
        {
            *this << int(n);
            n -= int(n);
            n *= 10;
        }
    }

    output& operator << (string n)
    {
        for (auto i : n)
            write(i);
        return *this;
    }
};

ifstream fin("fmcm.in");
output fout("fmcm.out");

vector <pair<int, int>> g[351];
int flow[351][351], n, m, Start, End;
int cap[351], d[351], t[351];
const int inf = 100000000;

void bfs()
{
    for (int i = 1; i <= n; i++)
        d[i] = inf;

    cap[Start] = inf;
    queue <int> Q;
    Q.push(Start);
    d[Start] = 0;

    while (!Q.empty())
    {
        int nod = Q.front();
        Q.pop();

        for (auto i : g[nod])
        {
            if (!flow[nod][i.first])
                continue;

            if (d[i.first] > d[nod] + i.second)
            {
                d[i.first] = d[nod] + i.second;
                cap[i.first] = min(cap[nod], flow[nod][i.first]);
                t[i.first] = nod;
                Q.push(i.first);
            }
        }
    }
}

int maxFlow()
{
    int cost = 0;

    while (true)
    {
        bfs();

        if (d[End] == inf)
            break;

        cost += d[End] * cap[End];

        int a, b = End;

        while (b != Start)
        {
            a = t[b];
            flow[a][b] -= cap[End];
            b = a;
        }
    }

    return cost;
}

int main()
{
    fin >> n >> m >> Start >> End;

    for (int i = 1; i <= m; i++)
    {
        int x, y, c, z;
        fin >> x >> y >> c >> z;

        g[x].push_back(make_pair(y, z));
        flow[x][y] = c;
    }

    fout << maxFlow();

    return 0;
}