using namespace std;
#include<iostream>
#include<fstream>
#include<vector>
#include<queue>
struct nod{
  int lg,c;
};
#define pb push_back
#define nmax 400
#define oo 0x3f3f3f3f
ofstream fout("fmcm.out");
vector<nod> G[nmax];
int N,M,S,D;
int C[nmax][nmax], F[nmax][nmax], ante[nmax];
int dp[nmax], isinq[nmax],viz[nmax];
bool BFS()
{
    int i;
    queue<int> q;
    for(i=0;i<=N;i++)
    {
        isinq[i]=0;
        dp[i]=oo;
        viz[i]=0;
    }
    q.push(S);
    isinq[S]=1;
    viz[S]=1;
    dp[S]=0;
    int u;
    vector<nod>::iterator it;
    while(!q.empty())
    {
        u=q.front();
        q.pop();
        isinq[u]=0;
        for(it=G[u].begin();it<G[u].end();it++)
        {
            if(C[u][it->lg]>F[u][it->lg])
             {
                  if(dp[it->lg]>dp[u]+it->c)
                  {   viz[it->lg]=1;
                      dp[it->lg]=dp[u]+it->c;
                      ante[it->lg]=u;
                      if(!isinq[it->lg])
                      {
                          q.push(it->lg);
                          isinq[it->lg]=1;
                      }
                  }

             }
        }
    }
    return viz[D];
}

void solve()
{
    int flow=0,i,ans=0,fmin=0;
    vector<nod>::iterator it;
    for(;BFS();)
    {
        fmin=C[ante[D]][D]-F[ante[D]][D];
        for(i=ante[D];i!=S;i=ante[i])
        {
            fmin=min(fmin,C[ante[i]][i]-F[ante[i]][i]);
        }

        F[ante[D]][D]+=fmin;
        F[D][ante[D]]-=fmin;

        for(i=ante[D];i!=S;i=ante[i])
        {
            F[ante[i]][i]+=fmin;
            F[i][ante[i]]-=fmin;
        }
        flow+=fmin;
        ans+=fmin*dp[D];
    }
    fout<<ans<<"\n";

}

void cit()
{
    ifstream fin("fmcm.in");
     int i,x,y,z,c;
    fin>>N>>M>>S>>D;
    for(i=1;i<=M;i++)
    {
        fin>>x>>y>>c>>z;
        G[x].pb((nod){y,z});
        G[y].pb((nod){x,-z});
        C[x][y]=c;

    }
    fin.close();
}

int main()
{
    cit();
    solve();
    fout.close();
    return 0;
}