#include<fstream>
#include<vector>
#include<deque>
#include<bitset>
using namespace std;
int n, m, x, y, a, cost, u, minim, s, d, i, sum;
int c[355][355], f[355][355], z[355][355], sd[355], t[355];
vector<int> v[355];
bitset<355> viz;
deque<int> cd;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
int bf(){
    int i, nod, vecin;
    int ok = 0;
    for(i = 1; i <= n; i++){
        sd[i] = 1000000000;
        viz[i] = 0;
    }
    cd.clear();
    viz[s] = 1;
    cd.push_back(s);
    sd[s] = 0;
    while( !cd.empty()){
        nod = cd.front();
        viz[nod] = 0;
        for(i = 0; i < v[nod].size(); i++){
            vecin = v[nod][i];
            if(sd[vecin] > sd[nod] + z[nod][vecin] && f[nod][vecin] < c[nod][vecin]){
                sd[vecin] = sd[nod] + z[nod][vecin];
                t[vecin] = nod;
                if(viz[vecin] == 0){
                    viz[vecin] = 1;
                    cd.push_back(vecin);
                }
                if(vecin == d){
                    ok = 1;
                }
            }
        }
        cd.pop_front();
    }
    return ok;
}
int main(){
    fin>> n >> m >> s >> d;
    for(i = 1; i <= m; i++){
        fin>> x >> y >> a >> cost;
        v[x].push_back(y);
        v[y].push_back(x);
        c[x][y] = a;
        z[x][y] = cost;
        z[y][x] = -cost;
    }
    while( bf() ){
        minim = 1000000000;
        for(u = d; t[u] > 0; u = t[u]){
            minim = min(minim, c[ t[u] ][u] - f[ t[u] ][u]);
        }

         for(u = d; t[u] > 0; u = t[u]){
            f[ t[u] ][u] += minim;
            f[u][ t[u] ] -= minim;
            sum += minim * z[ t[u] ][u];
        }
    }
    fout<< sum <<"\n";
    return 0;
}