#include <bits/stdc++.h>
#define oo 100000000

using namespace std;

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

vector<int> v[400];
queue<int> coada;
int C[400][400], F[400][400], cost[400][400];
int dist[400], TT[400], in_coada[400];
int drum, S, D, n, m;

int bellman_ford()
{
    int top, vec;
    for(int i=1; i<=n; i++)
    {
        dist[i] = oo;
        TT[i] = -1;
    }
    coada.push(S);
    coada.push(S);
    in_coada[S] = 1;
    dist[S] = 0;
    while(!coada.empty())
    {
        top = coada.front();
        for(int i=0; i<v[top].size(); i++)
        {
            vec = v[top][i];
            if(C[top][vec]-F[top][vec] > 0 && dist[vec] > dist[top] + cost[top][vec])
            {
                dist[vec] = dist[top] + cost[top][vec];
                TT[vec] = top;
                if(!in_coada[vec])
                {
                    coada.push(vec);
                    in_coada[vec] = 1;
                }
            }
        }
        coada.pop();
        in_coada[top] = 0;
    }

    if(dist[D] != oo)
    {
        int vmin = oo;
        drum = 1;
        for(int nod = D; nod!=S; nod = TT[nod])
            vmin = min(vmin, C[TT[nod]][nod] - F[TT[nod]][nod]);
        for(int nod = D; nod!=S; nod = TT[nod])
        {
            F[TT[nod]][nod] += vmin;
            F[nod][TT[nod]] -= vmin;
        }
        return vmin*dist[D];
    }
    return 0;
}

int flux()
{
    int rezultat = 0;
    drum = 1;
    while(drum)
    {
        drum = 0;
        rezultat += bellman_ford();
    }
    return rezultat;
}

int main()
{
    int x, y, c, z;
    fin >> n >> m >> S >> D;
    for(int i=1; i<=m;i++)
    {
        fin >> x >> y >> c >> z;
        v[x].push_back(y);
        v[y].push_back(x);
        C[x][y] = c;
        cost[x][y] = z;
        cost[y][x] = -z;
    }
    fout<<flux();
    return 0;
}