#include <bits/stdc++.h>

using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
const int nmax = 355;
const int inf = 2000000000;
int N,M,S,D,ans;
int dp[nmax],last[nmax];
int Cost[nmax][nmax],C[nmax][nmax],F[nmax][nmax];
bool viz[nmax];
vector < int > L[nmax];
queue < int > Q;

inline void Read()
{
    int i,j,x,y,z,c;
    fin >> N >> M >> S >> D;
    for(i = 1; i <= M; i++)
    {
        fin >> x >> y >> z >> c;
        Cost[x][y] = c; Cost[y][x] = -c;
        C[x][y] = z;
        L[x].push_back(y); L[y].push_back(x);
    }
}


inline bool Bellman()
{
    int i,nod;

    for(i = 1; i <= N; i++)
    {
        dp[i] = inf;
        last[i] = 0;
    }
    dp[S] = 0; viz[S] = true;
    Q.push(S);
    while(!Q.empty())
    {
        nod = Q.front();Q.pop();viz[nod] = false;
        for(auto it : L[nod])
        {
            if(F[nod][it] < C[nod][it] && dp[it] > dp[nod] + Cost[nod][it])
            {
                dp[it] = dp[nod] + Cost[nod][it];
                last[it] = nod;
                if(!viz[it])
                {
                    viz[it] = true;
                    Q.push(it);
                }
            }
        }
    }


    return (dp[D] != inf);
}


inline void Solve()
{
    int i,x,ccost,minflow,maxflow;
    while(Bellman())
    {
        ccost = 0;
        minflow = inf;
        for(x = D; x != S; x = last[x])
        {
            minflow = min(minflow,C[last[x]][x] - F[last[x]][x]);
            ccost += Cost[last[x]][x];
        }
        for(x = D; x != S; x = last[x])
        {
            F[last[x]][x] += minflow;
            F[x][last[x]] -= minflow;
        }
        ans += (minflow*ccost);
    }
    fout << ans << "\n";
    fout.close();
}


int main()
{
    Read();
    Solve();
    return 0;
}