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

#define nmax 352
#define inf 0x3f3f3f3f

int n, m, S, D, i, x, y, cap, ct, drum;
int d[nmax], df[nmax], db[nmax], t[nmax], c[nmax][nmax], viz[nmax], cst[nmax][nmax];
long long rez;

struct muchie
{
    int x, c;
};

struct cmp
{
    bool operator()(muchie x, muchie y)
    {
        return d[x.x] > d[y.x];
    }
};

vector <muchie> G[nmax];
queue <int> q;
priority_queue <muchie, vector<muchie>, cmp> pq;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

inline bool dijkstra()
{
    memset(d, inf, sizeof(d));
    d[S] = 0; df[S] = 0;
    pq.push({S,d[S]});

    while (!pq.empty())
    {
        int nod = pq.top().x;
        int cost = pq.top().c;
        pq.pop();

        if (d[nod] != cost)
            continue;

        for (auto &it : G[nod])
        {
            if (c[nod][it.x])
            {
                int dist = d[nod] + it.c + db[nod] - db[it.x];
                if (dist < d[it.x])
                {
                    d[it.x] = dist;
                    df[it.x] = df[nod] + it.c;
                    t[it.x] = nod;
                    pq.push({it.x, d[it.x]});
                }
            }
        }
    }

    memcpy(db, df, sizeof(d));
    if (d[D] == inf)
        return false;

    int fm = inf;
    for (int nod = D; nod != S; nod = t[nod])
        fm = min(fm, c[t[nod]][nod]);
    rez += fm * df[D];
    for (int nod = D; nod != S; nod = t[nod])
    {
        c[t[nod]][nod] -= fm;
        c[nod][t[nod]] += fm;
    }

    return true;
}

inline bool BellmanFord()
{
    memset(db, inf, sizeof(db));
    db[S] = 0;
    q.push(S);
    viz[S] = 1;

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

        for (auto &it : G[nod])
        {
            if (c[nod][it.x] && db[nod] + it.c < db[it.x])
            {
                db[it.x] = db[nod] + it.c;
                if (!viz[it.x])
                {
                    q.push(it.x);
                    viz[it.x] = 1;
                }
            }
        }

        viz[nod] = 0;
    }

    if (db[D] == inf)
        return false;

    return true;
}

int main()
{
    freopen("fmcm.in", "rt", stdin);
    freopen("fmcm.out", "wt", stdout);
    scanf("%d %d %d %d", &n, &m, &S, &D);


    for (i=1;i<=m;i++)
    {
        scanf("%d %d %d %d", &x, &y, &cap, &ct);
        c[x][y] = cap;
        G[x].push_back({y,ct});
        G[y].push_back({x,-ct});
        cst[x][y] = ct;
        cst[y][x] = -ct;
    }

    BellmanFord();

    while (dijkstra());

    printf("%d", rez);

    f.close();
    g.close();
    return 0;
}