#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>

using namespace std;

const int nmax = 355;
const int inf = (1LL << 31) - 1;

int i, n, m, s, d, x, y, z, t, ctotal, add;
int cap[nmax][nmax], cost[nmax][nmax];
int flow[nmax][nmax], dist[nmax], f[nmax];

vector<int> v[nmax];
deque<int> q;
bitset<nmax> inq;

bool bf()
{
    for(i = 1; i <= n; i++)
        dist[i] = inf;

    dist[s] = 0;
    f[s] = s;
    inq[s] = 1;
    q.push_back(s);

    while(!q.empty())
    {
        x = q.front();
        q.pop_front();
        inq[x] = 0;
        for(auto it : v[x])
            if(dist[x] + cost[x][it] < dist[it] && flow[x][it] < cap[x][it])
            {
                dist[it] = dist[x] + cost[x][it];
                f[it] = x;
                if(!inq[it])
                {
                    inq[it] = 1;
                    q.push_back(it);
                }
            }
    }

    return dist[d] != inf;
}
int main()
{
    freopen("fmcm.in", "r", stdin);
    freopen("fmcm.out", "w", stdout);

    scanf("%d%d%d%d", &n, &m, &s, &d);

    for(; m; m--)
    {
        scanf("%d%d%d%d", &x, &y, &z, &t);
        v[x].push_back(y);
        v[y].push_back(x);
        cap[x][y] = z;
        cost[x][y] = t;
        cost[y][x] = -t;
    }

    while(bf())
    {
        add = inf;
        for(x = d; x != f[x]; x = f[x])
            add = min(add, cap[f[x]][x] - flow[f[x]][x]);
        for(x = d; x != f[x]; x = f[x])
        {
            flow[f[x]][x] += add;
            flow[x][f[x]] -= add;
        }
        ctotal += dist[d] * add;
    }

    printf("%d\n", ctotal);

    return 0;
}