#include <bits/stdc++.h>

using namespace std;
int flux[1001][1001], capacitate[1001][1001];
deque <pair<int, int>> sol;
int tata[1001];
int s, d;
//int viz[1001];
int dist[1001];
int n;
vector <pair <int, int>> graf[1001];
bool maxflow (int nod)
{
    dist[nod] = 0;
    sol.push_back(make_pair(nod, 0));
    int verif = 0;
    while (!sol.empty())
    {
        int node = sol.front().first;
        int cost = sol.front().second;
        sol.pop_front();
        if (node == d)
        {
            verif = 1;
            continue;
        }
        for (auto x:graf[node])
        {
            if (capacitate[node][x.first]>flux[node][x.first] && dist[x.first]>dist[node]+x.second)
            {
                tata[x.first] = node;
                dist[x.first] = dist[node]+x.second;
                sol.push_back(make_pair(x.first, dist[x.first]));
            }
        }
    }
    return verif;
}
int main()
{
    ifstream fin ("fmcm.in");
    ofstream fout ("fmcm.out");
    int m, fluxul = 0;
    fin >> n >> m >> s >> d;
    for (int i = 1; i<=m; ++i)
    {
        int x, y, cap, cost;
        fin >> x >> y >> cap >> cost;
        graf[x].push_back(make_pair(y, cost));
        graf[y].push_back(make_pair(x, -cost));
        capacitate[x][y] += cap;
    }
    for (; maxflow(s);)
    {
        int minim = 1<<30;
        int copie = d;
        while (copie!=s)
        {
            if (minim > capacitate[tata[copie]][copie]-flux[tata[copie]][copie])
                minim = capacitate[tata[copie]][copie]-flux[tata[copie]][copie];
            copie = tata[copie];
        }
        if (minim == 0)
            continue;
        fluxul+=(minim*dist[d]);
        copie = d;
        while (copie!=s)
        {
            flux[tata[copie]][copie]+=minim;
            flux[copie][tata[copie]]-=minim;
            copie = tata[copie];
        }
        memset(tata, 0, sizeof(tata));
        memset(dist, 0x3f, sizeof(dist));
    }
    fout << fluxul;
    return 0;
}