#include <bits/stdc++.h>
#define DIM 352
#define inf 2000000000
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
int n,m,i,x,y,s,d,c,z,sol,fluxmin,nod,vecin,t[DIM],cap[DIM][DIM],dist[DIM],flux[DIM][DIM],cost[DIM][DIM];
bool v[DIM];
deque<int> q;
vector<int> L[DIM];
bool bf() {
    bool gasit=0;
    memset(v,0,sizeof(v));
    q.clear();
    for (i=1;i<=n;i++)
        dist[i]=inf;
    q.push_back(s);
    v[s]=1, dist[s]=0;
    while (!q.empty()) {
        nod=q.front();
        q.pop_front();
        v[nod]=0;
        for (i=0;i<L[nod].size();i++) {
            vecin=L[nod][i];
            if (cap[nod][vecin]>flux[nod][vecin]&&dist[vecin]>dist[nod]+cost[nod][vecin]) {
                t[vecin]=nod;
                dist[vecin]=dist[nod]+cost[nod][vecin];
                if (!v[vecin]) {
                    q.push_back(vecin);
                    v[vecin]=1;
                    if (vecin==d)
                        gasit=1;
                }
            }
        }
    }
    return gasit;
}
int main() {
    fin>>n>>m>>s>>d;
    for (i=1;i<=m;i++) {
        fin>>x>>y>>z>>c;
        L[x].push_back(y);
        L[y].push_back(x);
        cap[x][y]=z;
        cost[x][y]=c;
        cost[y][x]=-c;
    }
    while (bf()) {
        fluxmin=inf;
        nod=d;
        while (nod!=s) {
            fluxmin=min(fluxmin,cap[t[nod]][nod]-flux[t[nod]][nod]);
            nod=t[nod];
        }
        nod=d;
        while (nod!=s) {
            flux[t[nod]][nod]+=fluxmin;
            flux[nod][t[nod]]-=fluxmin;
            nod=t[nod];
        }
        sol+=fluxmin*dist[d];
    }
    fout<<sol;
    return 0;
}