#include <bits/stdc++.h>
using namespace std;

const int N = 360;
int n, m, t, s, cp[N][N], cost[N][N], d[N], d2[N], aux[N], pr[N], ans;
vector <int> v[N];
queue <int> Q;
bool u[N];
set <pair<int,int> > S;

void bellman(){
    for (int i=1; i<=n; i++) d[i] = 1e9;
    d[s] = 0;
    Q.push(s);
    while (!Q.empty()){
        int nod = Q.front();
        Q.pop();
        u[nod] = 0;
        for(auto it: v[nod]){
            if (!cp[nod][it]) continue;
            if (d[nod] + cost[nod][it] < d[it]){
                d[it] = d[nod] + cost[nod][it];
                if (!u[it]) u[it] = 1, Q.push(it);
            }
        }
    }
}

bool dijkstra(){
    for (int i=1; i<=n; i++) d2[i] = 1e9, pr[i] = 0;
    d2[s] = aux[s] = 0;
    S.insert({0, s});
    while (S.size()){
        int nod = S.begin()->second, costcr = S.begin()->first;
        S.erase(S.begin());
        if (costcr != d2[nod] || nod == t) continue;
        for (auto it: v[nod]){
            if (!cp[nod][it]) continue;
            if (d2[nod] + cost[nod][it] < d2[it]){
                d2[it] = d2[nod] + cost[nod][it];
                pr[it] = nod;
                S.insert({d2[it], it});
                aux[it] = aux[nod] + cost[nod][it];
            }
        }
    }
    return pr[t];
}

int main(){
    ifstream cin ("fmcm.in");
    ofstream cout ("fmcm.out");
    cin >> n >> m >> s >> t;
    for (int i=1, x, y, z, c; i<=m; i++){
        cin >> x >> y >> z >> c;
        v[x].push_back(y);
        cost[x][y] = c;
        cp[x][y] = z;
        v[y].push_back(x);
        cost[y][x] = -c;
    }
    bellman();
    while (dijkstra()){
        for (int i=1; i<=n; i++) d[i] = aux[i];
        int flux = 1e9;
        for (int nod = t; nod != s; nod = pr[nod])
            flux = min(flux, cp[pr[nod]][nod]);
        ans += d[t] * flux;
        for (int nod = t; nod != s; nod = pr[nod]){
            cp[pr[nod]][nod] -= flux;
            cp[nod][pr[nod]] += flux;
        }
    }
    cout << ans;
    return 0;
}