#include <cstdio>
#include <algorithm>
#include <vector>
#include <queue>

#define pii pair <int, int>
#define f first
#define s second

using namespace std;

int n, m, S, D;
vector <int> v[400];
int c[400][400], f[400][400], cost[400][400], t[400], drum[400];
bool inq[400];
queue <int> q;

inline bool bellman ()
{
    t[S] = -1;
    drum[S] = 0;
    q.push (S);
    inq[S] = true;
    bool OK = false;

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

        for (auto &it : v[nod])
            if (f[nod][it] < c[nod][it] && drum[nod] + cost[nod][it] < drum[it])
            {
                if (it == D)
                    OK = true;

                drum[it] = drum[nod] + cost[nod][it];
                t[it] = nod;

                if (!inq[it])
                    q.push (it),
                    inq[it] = true;
            }

        inq[nod] = 0;
    }

    return OK;
}

int main ()
{
    freopen ("fmcm.in", "r", stdin);
    freopen ("fmcm.out", "w", stdout);

    scanf ("%d %d %d %d", &n, &m, &S, &D);

    for (int i = 1; i <= m; ++i)
    {
        int x, y, costt, cap;
        scanf ("%d %d %d %d", &x, &y, &cap, &costt);

        v[x].push_back (y);
        v[y].push_back (x);

        c[x][y] = cap;
        cost[x][y] = costt;
        cost[y][x] = -costt;
    }

    for (int i = 1; i <= n; ++i)
        drum[i] = 2000000000;

    long long cos = 0LL;
    for (; bellman ();)
    {
        int nod = D, mi = 2000000000;

        for (; t[nod] != -1; nod = t[nod])
            mi = min (mi, c[t[nod]][nod] - f[t[nod]][nod]);

        nod = D;
        for (; t[nod] != -1; nod = t[nod])
            f[t[nod]][nod] += mi,
            f[nod][t[nod]] -= mi,
            cos += 1LL * mi * cost[t[nod]][nod];

        for (int i = 1; i <= n; ++i)
            t[i] = 0, drum[i] = 2000000000, inq[i] = false;
    }

    printf ("%lld\n", cos);

    return 0;
}