#include <cstdio>
#include <cstring>
#include <queue>
#include <utility>
#include <vector>

using namespace std;

const int N = 355, inf = (1ll << 31) - 1;

vector <int> graph [N];
int f [N][N], c [N][N], cost [N][N], l [N], father [N];
bool in_q [N];
int n;

bool bellmanford (int s, int d) {
    int i;
    queue <int> q;
    vector <int> :: iterator it;

    for (i = 1; i <= n; i ++)
        l [i] = inf;
    memset (in_q, 0, sizeof (in_q));
    q.push (s);
    in_q [s] = 1;
    l [s] = 0;
    while (!q.empty ()) {
        i = q.front ();
        q.pop ();
        for (it = graph [i].begin (); it != graph [i].end (); ++ it)
            if (c [i][*it] - f [i][*it] > 0)
                if (l [*it] > l [i] + cost [i][*it]) {
                    l [*it] = l [i] + cost [i][*it];
                    father [*it] = i;
                    if (in_q [*it] == 0) {
                        q.push (*it);
                        in_q [*it] = 1;
                    }
                }
        in_q [i] = 0;
    }
    if (l [d] != inf)
        return 1;
    return 0;
}

int main () {
    int i, x, y, cap, z, s, d, ans = 0, m, minflow;

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

    scanf ("%d%d%d%d", &n, &m, &s, &d);
    for (i = 1; i <= m; i ++) {
        scanf ("%d%d%d%d", &x, &y, &cap, &z);
        c [x][y] = cap;
        cost [x][y] = z;
        cost [y][x] = -z;
        graph [x].push_back (y);
        graph [y].push_back (x);
    }
    while (bellmanford (s, d)) {
        minflow = inf;
        for (i = d; i != s; i = father [i])
            minflow = min (minflow, c [father [i]][i] - f [father [i]][i]);
        if (minflow == 0)
            continue;
        for (i = d; i != s; i = father [i]) {
            f [father [i]][i] += minflow;
            f [i][father [i]] -= minflow;
            ans = ans + minflow * cost [father [i]][i];
        }
    }
    printf ("%d\n", ans);
    return 0;
}