#include <bits/stdc++.h>
#define MAXN 350
#define INF 1000000000

int n, m, S, D, total;
std::vector <int> G[1 + MAXN];
int C[1 + MAXN][1 + MAXN], Cost[1 + MAXN][1 + MAXN];
int father[1 + MAXN];

int q[1 + MAXN * MAXN], p, u, inq[1 + MAXN];
int dist[1 + MAXN];
inline void bellmanFord(){
    for(int i = 1; i <= n; i++) dist[i] = INF;
    p = u = 0;
    q[u++] = S, inq[S] = 1, dist[S] = 0;
    while(p < u){
        int node = q[p++];
        inq[node] = 0;
        for(auto y:G[node])
            if(C[node][y] && dist[y] > dist[node] + Cost[node][y]){
                dist[y] = dist[node] + Cost[node][y];
                if(!inq[y]) inq[y] = 1, q[u++] = y;
            }
    }
}

int d[1 + MAXN], reald[1 + MAXN];
std::priority_queue <std::pair<int, int>, std::vector<std::pair<int, int>>, std::greater<std::pair<int, int>>> pq;
inline bool dijkstra(){
    for(int i = 1; i <= n; i++) d[i] = INF;
    d[S] = 0, reald[S] = 0;
    pq.push({0, S});
    while(!pq.empty()){
        int node = pq.top().second, cost = pq.top().first;
        pq.pop();
        if(d[node] == cost){
            for(auto y: G[node])
                if(C[node][y]){
                    int newd = d[node] + Cost[node][y] + dist[node] - dist[y];
                    if(newd < d[y]){
                        d[y] = newd;
                        reald[y] = reald[node] + Cost[node][y];
                        father[y] = node;
                        pq.push({d[y], y});
                    }
                }
        }
    }
    memcpy(dist, reald, n);
    return (d[D] != INF);
}

int main(){
    FILE*fi,*fo;
    fi = fopen("fmcm.in","r");
    fo = fopen("fmcm.out","w");

    fscanf(fi,"%d%d%d%d", &n, &m, &S, &D);
    for(int i = 1; i <= m; i++){
        int x, y, capacity, cost;
        fscanf(fi,"%d%d%d%d", &x, &y, &capacity, &cost);
        G[x].push_back(y);
        G[y].push_back(x);
        C[x][y] += capacity;
        Cost[x][y] += cost;
        Cost[y][x] -= cost;
    }

    bellmanFord();
    while(dijkstra()){
        int flow = INF, cost = 0;
        for(int i = D; i != S; i = father[i]) flow = std::min(flow, C[father[i]][i]), cost += Cost[father[i]][i];
        for(int i = D; i != S; i = father[i]) C[father[i]][i] -= flow, C[i][father[i]] += flow;
        total += cost * flow;
    }
    fprintf(fo,"%d", total);

    return 0;
}