#include <iostream>
#include <fstream>
using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

#define x first
#define y second
#define mp make_pair
#define pii pair<int,int>
#define inf (1<<30)
#define LE 366
#define R return
#include <iostream>

int nod;
int dp[LE],father[LE],que[LE*66];
pii cap[LE][LE];
int  S,D,k,i,j,n,m;
int result,fres;

bool Flux() {
    que[(k=1)]=S;
    for(i=1; i<=n; ++i) dp[i]=inf,father[i]=0;
    dp[S]=-inf;

    for(i=1; i<=k; ++i) {
        for(j=1; j<=n; ++j)
            if (cap[que[i]][j].x>0)
                if (dp[j]>dp[que[i]]+cap[que[i]][j].y) {
                    dp[j]=dp[que[i]]+cap[que[i]][j].y;
                    father[j]=que[i];
                    que[++k]=j;
                }
    }
    if (dp[D]==inf) R false;
    R true;
}

int main() {

    f>>n>>m>>S>>D;
    for(i=1; i<=m; ++i) {
        int xx,yy,cp,cc;
        f>>xx>>yy>>cp>>cc;
        cap[xx][yy]=mp(cp,cc);
        cap[yy][xx]=mp(0,-cc);
    }

    while (Flux()){
       int fmax=inf;
       nod=D;
       //cout<<-1<<'\n';
       //for(i=1;i<=n;++i) cout<<father[i]<<" ";
       //cout<<'\n';
      while (father[nod]!=0){
        fmax=min(fmax,cap[father[nod]][nod].x);
        nod=father[nod];
       // cout<<nod<<" ";
      }
      //cout<<-1;
      nod=D;
      while (father[nod]!=0){
        cap[father[nod]][nod].x-=fmax;
        cap[nod][father[nod]].x+=fmax;
        result+=cap[father[nod]][nod].y*fmax;
        nod=father[nod];
      }
      fres+=fmax;
    }

    g<<result<<'\n';


    f.close();
    g.close();
    return 0;
}