#include <bits/stdc++.h>

using namespace std;

FILE *F=fopen("fmcm.in", "r"), *G=fopen("fmcm.out", "w");

const int N = 360;
const int inf = 0x3f3f3f3f;
priority_queue<pair<int, int> > pq;
queue<int> q;

int n, m, s, d, x, y, z, c;
int f[N][N];
int C[N][N];
int cost[N][N];
int olDist[N];
int dist[N];
int realDist[N];
vector<int> a[N];
int sol = 0, Fmin;
int t[N];
int cq[N];
bitset<N> w;

int dijkstra()
{
    for(int i = 1; i <= n; ++ i) dist[i] = inf;
    pq.push({0, s});
    t[s] = s;
    dist[s] = 0;
    realDist[s] = 0;
    w = 0;
    while(!pq.empty())
    {
        x = pq.top().second;
        pq.pop();
        if(w[x]) continue;
        w[x] = 1;
        for(int i = 0; i < a[x].size(); ++ i)
        {
            y = a[x][i];
            if(f[x][y] < C[x][y])
            {
                if(dist[y] > dist[x] + cost[x][y] + olDist[x] - olDist[y])
                    dist[y] = dist[x] + cost[x][y] + olDist[x] - olDist[y], t[y] = x, pq.push({-dist[y], y}), realDist[y] = cost[x][y]+realDist[x];
            }
        }
    }
    return (dist[d] != inf);
}

int main()
{
    fscanf(F, "%d %d %d %d ", &n, &m, &s, &d);
    for(int i = 0; i < m; ++ i)
    {
        fscanf(F, "%d %d %d %d ", &x, &y, &c, &z);

        a[x].push_back(y);
        a[y].push_back(x);
        C[x][y] = c;
        cost[x][y] = z;
        cost[y][x] = -z;
    }
    for(int i = 1; i <= n; ++ i) olDist[i] = inf;
    q.push(s);
    cq[s] = 1;  olDist[s] = 0;
    while(!q.empty())
    {
        x = q.front();
        q.pop();
        cq[x] = 0;
        for(int i = 0; i < a[x].size(); ++ i)
        {
            y = a[x][i];
            if(f[x][y] < C[x][y] && olDist[y] > cost[x][y] + olDist[x])
            {
                olDist[y] = cost[x][y] + olDist[x];
                if(!cq[y]) q.push(y), cq[y] = 1;
            }
        }
    }
    while(dijkstra())
    {
        Fmin = inf;
        for(int i = d; i != s; i = t[i])
            Fmin = min(Fmin, C[t[i]][i] - f[t[i]][i]);

        sol += realDist[d] * Fmin;

        if(!Fmin) continue;
        for(int i = d; i != s; i = t[i]) f[t[i]][i] += Fmin, f[i][t[i]] -= Fmin;

        for(int i = 1; i <= n; ++ i) olDist[i] = realDist[i];
    }
    fprintf(G, "%d", sol);
    return 0;
}