#include <cstdio>
#include <cstring>
#include <vector>
#include <set>
using namespace std;
#define MAX 1001
#define INF 0xfffffff

vector<int>g[MAX];
set<int>s1,s2;

int n,m,s,d,c[MAX][MAX],f[MAX][MAX],p[MAX][MAX],dist[MAX],tt[MAX];

bool drum(){
    int x,y;
    for(int i=1;i<=n;i++)
    {
        dist[i] = INF;
        tt[i] = 0;
    }
        dist[s] = 0;

    s1.insert(s);
    for(int i=1;i<=n;i++)
    {
        while(s1.size() > 0)
        {
        x = *s1.begin(); s1.erase(s1.begin());
        for(int i=0;i<g[x].size();i++)
        {
            y = g[x][i];
            if( dist[y] > dist[x] + p[x][y] && c[x][y] > f[x][y] )
            {
                dist[y] = dist[x] + p[x][y];
                tt[y] = x;
                s2.insert(y);
            }
        }
        }
        swap(s1,s2);
    }
  //  for(int i=1;i<=n;i++)printf("%d ",dist[i]);
   // printf("\n");
   if( dist[d] != INF )return 1; else return 0;
}
/*
bool drum(){
    int y;
    for(int i=1;i<=n;i++)
    {
        dist[i] = INF;
        tt[i] = 0;
    }
        dist[s] = 0;

    for(int k=1;k<=n;k++)
    {
        for(int i=1;i<=n;i++)
        for(int j=0;j<g[i].size();j++)
        {
            y = g[i][j];
            if( dist[y] > dist[i] + p[i][y] && c[i][y] > f[i][y] )
            {
                dist[y] = dist[i] + p[i][y];
                tt[y] = i;
            }
        }
    }
  //  for(int i=1;i<=n;i++)printf("%d ",dist[i]);
   // printf("\n");
    if( dist[d] < INF/2 )return 1; else return 0;
}
*/
void maxflow(){
    int fmcm = 0, flux; int step = 0;
    while( drum() )
    {
        flux = INF;
        for(int x = d; x != s;x = tt[x]) flux = min(flux, c[tt[x]][x]-f[tt[x]][x]);
        for(int x = d; x != s;x = tt[x])
            {
                f[tt[x]][x] += flux;
                f[x][tt[x]] -= flux;
                fmcm += flux * p[tt[x]][x];
            }
       // for(int i=1;i<=n;i++){ for(int j=1;j<=n;j++) printf("%d ",f[i][j]); printf("\n"); }
    }
    printf("%d\n",fmcm);
}

int main(){
    int x,y,z,w;
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
        scanf("%d %d %d %d",&n,&m,&s,&d);

        for(int i=1;i<=m;i++)
        {
            scanf("%d %d %d %d",&x,&y,&z,&w);
            g[x].push_back(y);
            g[y].push_back(x);
            c[x][y] = z;
            p[x][y] = w;
            p[y][x] = -w;
        }

    maxflow();
    return 0;
}