#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

#define nmax 351
#define Mmax 12505
#define inf (1<<30)

int n, m, S, D, dist[nmax], cost[nmax][nmax], capac[nmax][nmax], flux[nmax][nmax], t[nmax];
bool viz[nmax];
vector<int> gf[nmax];
int q[nmax+Mmax];

void citeste(){
    f >> n >> m >> S >> D;
    int x, y, c, z;
    for(int i=1; i<=m; ++i){
        f >> x >> y >> c >> z;
        gf[x].push_back(y);
        gf[y].push_back(x);
        capac[x][y] = c; cost[x][y] = z; cost[y][x] = -z;
    }
}

inline int bf(int S, int D){
    for(int i=0; i<nmax; ++i) viz[i] = 0, dist[i] = inf;
    dist[S] = 0;
    int st = 1; int dr = 0;
    q[++dr] = S; viz[S] = 1;

    for(; st<=dr; ){
        int nod = q[st]; ++st;
        viz[nod] = 0;
        for(int i=0; i<gf[nod].size(); ++i){
            int vc = gf[nod][i];
            if (dist[vc] > dist[nod] + cost[nod][vc] && capac[nod][vc] > flux[nod][vc]){
                t[vc] = nod;
                dist[vc] = dist[nod] + cost[nod][vc];
                if (viz[vc] == 0){
                    viz[vc] = 1; q[++dr] = vc;
                }
            }
        }
    }

    return dist[D];
}

void rezolva(){
    int Flux = 0;
    for(int ok=1; ok!=0; ){
        int Cost = bf(S, D);
        if (Cost == inf) break;
        int Min = inf;
        for(int i=D; i!=S; i=t[i]){
            Min = min(Min, capac[ t[i] ][i] - flux[ t[i] ][i]);
        }
        for(int i=D; i!=S; i=t[i]){
            flux[ t[i] ][i] += Min;
            flux[i][ t[i] ] -= Min;
        }
        Flux += Min * Cost;
    }
    cout << Flux << "\n";
    g << Flux << "\n";
}

int main(){
    citeste();
    rezolva();

    f.close();
    g.close();

    return 0;
}