#include <iostream>
#include <fstream>
#include <queue>
#include <vector>
#define nmax 400
#define inf 1e9
using namespace std;
ifstream f("fmcm.in");
ofstream g("fmcm.out");
int n,m, start, stop;
int d[nmax], dist[nmax], viz[nmax], t[nmax], ans[nmax];
int cp[nmax][nmax], fx[nmax][nmax], ct[nmax][nmax];
vector <int> v[nmax];
queue  <int> q;
priority_queue< pair <int,int> > pq;
void citire()
{
    int i,j,k,c,z;
    f>> n >> m >> start >> stop;
    for(k=1; k<=m; k++)
    {
        f>>i>>j>>c>>z;
        v[i].push_back(j);
        v[j].push_back(i);
        cp[i][j]=c;
        ct[i][j]=z; ct[j][i]=-z;
    }
}

void bellman()
{
    int i, nod;
    for(i=1; i<=n; i++)
        d[i]=inf;
    q.push(start);
    d[start]=0;
    while(!q.empty())
    {
       nod = q.front();
       q.pop();
       viz[nod]++;
       if(viz[nod]==n)
        return;
       for(i=0; i<v[nod].size(); i++)
        if(d[v[nod][i]]>d[nod]+ct[nod][v[nod][i]] && fx[nod][v[nod][i]]<=cp[nod][v[nod][i]])
       {
           d[v[nod][i]]=d[nod]+ct[nod][v[nod][i]];
           q.push(v[nod][i]);
       }
    }
}

int dijkstra()
{
    int i, nod;
    while(!pq.empty()) pq.pop();
    for(i=1; i<=n; i++)
        dist[i]=inf;
    pq.push({0,start});
    viz[start]=1;
    while(!pq.empty())
    {
        nod=pq.top().second;
        pq.pop();
        for(i=0; i<v[nod].size(); i++)
        {  int newd=dist[nod]+ ct[nod][v[nod][i]] + d[nod] - d[v[nod][i]];
            if(fx[nod][v[nod][i]]<=cp[nod][v[nod][i]] && newd<dist[v[nod][i]])
                {
                    dist[v[nod][i]]=newd;
                    ans[v[nod][i]]=ans[nod] + ct[nod][v[nod][i]];
                    t[v[nod][i]]=nod;
                    pq.push({-dist[v[nod][i]], v[nod][i]});
                }
        }
    }
    for(i=1; i<=n; i++)
        d[i]=ans[i];
    return (dist[n]!=inf);
}


int main()
{
    int fmin,i, cost;
    citire();
    bellman();
    while(dijkstra())
    {
        fmin=inf;
        for(i=stop; i!=start; i=t[i])
            fmin=min(cp[t[i]][i]-fx[t[i]][i], fmin);
        for(i=stop; i!=start; i=t[i])
        {
            fx[i][t[i]]+=fmin;
            fx[t[i]][i]-=fmin;
        }
       cost= fmin*d[n];
    }
    g<<cost;
    f.close();
    g.close();
    return 0;
}