#include <bits/stdc++.h>
#define DIM 353
#define inf 200000000
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
deque <int> q;
vector <int> L[DIM];
bitset<DIM> v;
int n,x,y,s,d,m,fsol,z,c,nod,vecin,cap[DIM][DIM],flux[DIM][DIM],i,fluxmin,t[DIM],cost[DIM][DIM],gasit,dist[DIM];
bool bf() {
    v.reset();
    for(i=1;i<=n;i++)
        dist[i]=inf;
    dist[s]=0, v[s]=1;
    gasit=0;
    q.clear();
    q.push_back(s);
    while(!q.empty()) {
        nod=q.front();
        q.pop_front();
        v[nod]=0;
        for(int 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]) {
                dist[vecin] = dist[nod]+cost[nod][vecin];
                t[vecin]=nod;
                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()) {
        nod=d;
        fluxmin=inf;
        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];
        }
        fsol+=fluxmin*dist[d];
    }
    fout<<fsol<<"\n";
}