#include <bits/stdc++.h>

using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
typedef pair<int,int> pii;
const int INF=1e9;
int n,m,cap[355][355],cost[355][355],pred[355],dist[355],dijk[355],d[355],fcost,S,D;
vector<int> muchii[355];
bool viz[355];
void bellman()
{
    for(int i=1;i<=n;i++)
        dist[i]=INF;
    dist[S]=0;
    queue<int> q;
    q.push(S);
    while(!q.empty())
    {
        int nod=q.front();
        q.pop();
        for(int i:muchii[nod])
            if(cap[nod][i]>0&&dist[i]>dist[nod]+cost[nod][i])
            {
                dist[i]=dist[nod]+cost[nod][i];
                q.push(i);
            }
    }
}
struct comp
{
    bool operator()(pii a, pii b)
    {
        return a.first>b.first;
    }
};
bool flux()
{
    for(int i=1;i<=n;i++)
    {
        d[i]=INF;
        dijk[i]=INF;
        pred[i]=0;
        viz[i]=0;
    }
    d[S]=0;
    dijk[S]=0;
    priority_queue<pii, vector<pii>, comp> pq;
    pq.push({0,S});
    while(!pq.empty())
    {
        int nod=pq.top().second;
        pq.pop();
        if(viz[nod])
            continue;
        viz[nod]=1;
        for(int i:muchii[nod])
            if(cap[nod][i]>0&&d[i]>d[nod]+cost[nod][i]+dist[nod]-dist[i])
            {
                d[i]=d[nod]+cost[nod][i]+dist[nod]-dist[i];
                dijk[i]=dijk[nod]+cost[nod][i];
                pred[i]=nod;
                pq.push({d[i],i});
            }
    }
    for(int i=1;i<=n;i++)
        dist[i]=dijk[i];
    if(dijk[D]==INF)
        return 0;
    int minim=1e9;
    for(int i=D;i!=S;i=pred[i])
        minim=min(minim,cap[pred[i]][i]);
    fcost+=minim*dijk[D];
    for(int i=D;i!=S;i=pred[i])
    {
        cap[pred[i]][i]-=minim;
        cap[i][pred[i]]+=minim;
    }
    return 1;
}
int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);
    fin>>n>>m>>S>>D;
    for(int i=1;i<=m;i++)
    {
        int a,b,c,d;
        fin>>a>>b>>c>>d;
        muchii[a].push_back(b);
        muchii[b].push_back(a);
        cap[a][b]=c;
        cost[a][b]=d;
        cost[b][a]=-d;
    }
    bellman();
    while(flux());
    fout<<fcost;
    return 0;
}