#include <fstream>
#include <vector>
#include <deque>
#include <bitset>
#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,fmin,nod,vecin,t[DIM],cap[DIM][DIM],dist[DIM],flux[DIM][DIM],cost[DIM][DIM];
bitset<DIM> v;
deque<int> q;
vector<int> L[DIM];
bool bf() {
    bool gasit=0;
    v.reset();
    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()) {
        fmin=inf;
        for (nod=d;nod!=s;nod=t[nod])
            fmin=min(fmin,cap[t[nod]][nod]-flux[t[nod]][nod]);
        for (nod=d;nod!=s;nod=t[nod]) {
            flux[t[nod]][nod]+=fmin;
            flux[nod][t[nod]]-=fmin;
        }
        sol+=fmin*dist[d];
    }
    fout<<sol;
    return 0;
}