#include <iostream>
#include <vector>
#include <cstdio>
#include <queue>

using namespace std;

typedef long long ll;
const int N = 350;
const int INF = (int) 1e9;
int n;
int m;
int s;
int d;
int cap[N][N];
int cost[N][N];
vector<int> g[N];
int best[N];
int par[N];
bool act[N];

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

    cin >> n >> m >> s >> d;
    s--;
    d--;
    for (int i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        a--;
        b--;
        g[a].push_back(b);
        b[g].push_back(a);
        cin >> cap[a][b] >> cost[a][b];
        cost[b][a] = -cost[a][b];
    }
    ll ans = 0;
    while (1)
    {
        for (int i = 0; i < n; i++)
        {
            best[i] = INF;
        }
        act[s] = 1;
        best[s] = 0;
        queue<int> q;
        q.push(s);
        while (!q.empty())
        {
            int a = q.front();
            q.pop();
            act[a] = 0;
            for (auto &b : g[a])
            {
                if (cap[a][b] > 0 && best[a] + cost[a][b] < best[b])
                {
                    best[b] = best[a] + cost[a][b];
                    par[b] = a;
                    if (act[b] == 0)
                    {
                        act[b] = 1;
                        q.push(b);
                    }
                }
            }
        }
        if (best[d] == INF)
        {
            break;
        }
        int mn = INF, now = d;
        while (now != s)
        {
            int a = par[now];
            int b = now;
            mn = min(mn, cap[a][b]);
            now = par[now];
        }
        ans += (ll) best[d] * mn;
        now = d;
        while (now != s)
        {
            int a = par[now];
            int b = now;
            cap[a][b] -= mn;
            cap[b][a] += mn;
            now = par[now];
        }
    }
    cout << ans << "\n";
}