#include<fstream>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;
#define INF 0x3f3f3f3f
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
vector <int> v[355];
queue <int> q;
int n,m,s,d,x,y,z,c,minim,cost,D[355],T[355],C[355][355],F[355][355],Z[355][355];
bool bellman_ford()
{
    int i;
    memset(D,0x3f,sizeof(D));
    D[s]=0;
    q.push(s);
    while (!q.empty())
    {
        x=q.front(); q.pop();
        for (i=0;i<v[x].size();++i)
        {
            y=v[x][i], z=Z[x][y];
            if (D[y]>D[x]+z && C[x][y]>F[x][y])
            {
                D[y]=D[x]+z;
                T[y]=x;
                q.push(y);
            }
        }
    }
    return (D[d]!=INF);
}
int main()
{
    int i;
    fin>>n>>m>>s>>d;
    for (i=1;i<=m;++i)
    {
        fin>>x>>y>>c>>z;
        v[x].push_back(y);
        v[y].push_back(x);
        C[x][y]=c;
        Z[x][y]=z, Z[y][x]=-z;
    }
    while (bellman_ford())
    {
        minim=INF, x=d;
        while (x!=s)
        {
            minim=min(minim,C[T[x]][x]-F[T[x]][x]);
            x=T[x];
        }
        x=d;
        while (x!=s)
        {
            F[T[x]][x]+=minim, F[x][T[x]]-=minim;
            x=T[x];
        }
        cost+=D[d]*minim;
    }
    fout<<cost<<"\n";
    return 0;
}