#include <bits/stdc++.h>
#define inf 2e9

using namespace std;

ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

const int nmax = 355;

int n, m, s, d;
int cap[nmax][nmax], cost[nmax][nmax], f[nmax][nmax];
int cst[nmax], tt[nmax];
bool ok, vis[nmax];
vector <int> v[nmax];

void read(){
    fin >> n >> m >> s >> d;

    for(int i = 1; i <= m; i++){
        int x, y, c, z;
        fin >> x >> y >> c >> z;
        v[x].push_back(y);
        v[y].push_back(x);
        cap[x][y] = c;
        cost[x][y] = z;
        cost[y][x] = -z;
    }
}

int bellmanFord(){
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; i++){
        cst[i] = inf;
        tt[i] = -1;
    }

    vector <int> q;
    q.push_back(s);
    cst[s] = 0;
    vis[s] = 1;

    for(int i = 0; i < q.size(); i++){
        int x = q[i];

        for(int j = 0; j < v[x].size(); j++){
            int y = v[x][j];
            if(cap[x][y] - f[x][y] > 0 && cst[x] + cost[x][y] < cst[y]){
                cst[y] = cst[x] + cost[x][y];
                tt[y] = x;
                if(!vis[y]){
                    q.push_back(y);
                    vis[y] = 1;
                }
            }
        }

        vis[x] = 0;
    }

    if(cst[d] != inf){
        int fluxMin = inf;
        ok = 1;

        for(int i = d; i != s; i = tt[i])
            fluxMin= min(fluxMin, cap[tt[i]][i] - f[tt[i]][i]);
        for(int i = d; i != s; i = tt[i]){
            f[tt[i]][i] += fluxMin;
            f[i][tt[i]] -= fluxMin;
        }

        return fluxMin * cst[d];
    }

    return 0;
}

void solve(){
    int cost_min = 0;
    ok = 1;

    while(ok){
        ok = 0;
        cost_min += bellmanFord();
    }

    fout << cost_min;
}

int main()
{
    read();
    solve();

    return 0;
}