#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <bitset>
#define MAXN 360
#define inf 0x3f3f3f3f

using namespace std;

int n, m, s, d;
int cost[MAXN][MAXN], capac[MAXN][MAXN], flux[MAXN][MAXN];
vector<int> graf[MAXN];

void citire()
{
    scanf("%d %d %d %d", &n, &m, &s, &d);
    for (int i = 1; i <= m; i++) {
        int x, y, c, z;
        scanf("%d %d %d %d", &x, &y, &c, &z);
        capac[x][y] = c;
        cost[x][y] = z;
        cost[y][x] = -z;
        graf[x].push_back(y);
        graf[y].push_back(x);
    }
}

queue<int> q;
bitset<MAXN> inq;
int best[MAXN];

void bellman()
{
    for (int i = 0; i <= n; i++)
        best[i] = inf;
    q.push(s);
    best[s] = 0;
    while (!q.empty()) {
        int top = q.front();
        q.pop();
        for (int y : graf[top]) {
            if (capac[top][y] > flux[top][y] && best[top]+cost[top][y] < best[y]) {
                best[y] = best[top] + cost[top][y];
                if (!inq[y])
                    q.push(y);
            }
        }
    }
}
int djmi[MAXN], parent[MAXN], real[MAXN];
struct cmp
{
    bool operator()(const int &x, const int &y) const
    {
        return djmi[x] > djmi[y];
    }
};
priority_queue<int, vector<int>, cmp> heap;

int dijkstra()
{
    for (int i = 0; i <= n; i++)
        djmi[i] = inf;
    heap.push(s);
    djmi[s] = 0;
    while (!heap.empty()) {
        int top = heap.top();
        heap.pop();
        for (int y : graf[top]) {
            int nc = cost[top][y] + best[top] - best[y];
            if (capac[top][y] > flux[top][y] && djmi[top]+nc < djmi[y]) {
                djmi[y] = djmi[top] + nc;
                real[y] = real[top] + cost[top][y];
                parent[y] = top;
                heap.push(y);
            }
        }
    }
    return (djmi[d] != inf);
}

int rez = 0;
void solve()
{
    for (bellman(); dijkstra(); ) {
        int mini = inf, cost = 0;
        for (int y = d; y != s; y = parent[y])
            mini = min(mini, capac[parent[y]][y] - flux[parent[y]][y]);
        for (int y = d; y != s; y = parent[y]) {
            flux[parent[y]][y] += mini;
            flux[y][parent[y]] -= mini;
        }
        rez += mini*real[d];
        for (int i = 1; i <= n; i++)
            best[i] = real[i];
    }
}

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

    citire();
    solve();
    printf("%d", rez);

    return 0;
}