#include <bits/stdc++.h>
//maybeeee we'll meet at a baaaar, we'll drivee a funky hhhhhhuuugh

using namespace std;
ifstream fin ("fmcm.in");
ofstream fout ("fmcm.out");
int n, m, s, D, maxflux, cost;
struct much{
    int a, b, c, z, f, per;
};
much a[24005];
vector <int> v[355];
int d[355], dvechi[355], reald[355], last[355];

void omul_cu_clopot(){
    for(int i = 1; i <= n; i++){
        reald[i] = INT_MAX;
    }
    reald[s] = 0;
    for(int i = 1; i < n; i++){
        for(int j = 1; j <= 2 * m; j++){
            reald[a[j].b] = min(reald[a[j].b], reald[a[j].a] + a[j].z);
        }
    }
}

void deschistra(){
    priority_queue < pair <int, int>, vector < pair <int, int> >, greater < pair <int, int> > > q;
    for(int i = 1; i <= n; i++){
        dvechi[i] = reald[i];
        d[i] = INT_MAX;
        last[i] = -1;
    }
    d[s] = 0;
    reald[s] = 0;
    last[s] = 0;
    q.push({0, s});
    int nod, dnou;
    much nxt;
    while(!q.empty()){
        dnou = q.top().first;
        nod = q.top().second;
        q.pop();
        if(dnou != d[nod]){
            continue;
        }
        for(int i = 0; i < v[nod].size(); i++){
            nxt = a[v[nod][i]];
            if(dnou + nxt.z + dvechi[nxt.a] - dvechi[nxt.b] < d[nxt.b] &&
               nxt.f < nxt.c && nod != D){
                last[nxt.b] = v[nod][i];
                d[nxt.b] = dnou + nxt.z + dvechi[nxt.a] - dvechi[nxt.b];
                reald[nxt.b] = reald[nod] + nxt.z;
                q.push({d[nxt.b], nxt.b});
            }
        }
    }
}

void fa_un_drum(){
    int nod = D, minim_ude = INT_MAX;
    while(last[nod] != 0){
        minim_ude = min(minim_ude, a[last[nod]].c - a[last[nod]].f);
        nod = a[last[nod]].a;
    }
    maxflux += minim_ude;
    cost += minim_ude * reald[D];
    nod = D;
    while(last[nod] != 0){
        a[last[nod]].f += minim_ude;
        a[a[last[nod]].per].f -= minim_ude;
        nod = a[last[nod]].a;
    }
}

void flux(){
    int lastflux = -1;
    while(lastflux != maxflux){
        lastflux = maxflux;
        deschistra();
        if(last[D] != -1){
            fa_un_drum();
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    fin >> n >> m >> s >> D;
    for(int i = 1; i <= m; i++){
        fin >> a[i].a >> a[i].b >> a[i].c >> a[i].z;
    }
    for(int i = 1; i <= m; i++){
        a[i].per = i + m;
        a[i+m] = {a[i].b, a[i].a, 0, -a[i].z, i};
        v[a[i].a].push_back(i);
        v[a[i].b].push_back(i + m);
    }
    omul_cu_clopot();
    flux();
    fout << cost;
    return 0;
}