//#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream in("fmcm.in");
ofstream out("fmcm.out");
int n,m,s,d,k;
const int Max=350;
int c[Max][Max],tata[Max],dist[Max],incoada[Max];
vector <pair <int,int> >v[Max];
struct compara
{
    bool operator()(int x,int y)
    {
        return dist[x]>dist[y];
    }
};
priority_queue <int,vector<int>,compara>q;
void citire()
{
   in>>n>>m>>s>>d;
   for(int i=1;i<=m;i++)
   {
       int x,y,cap,cost;
       in>>x>>y>>cap>>cost;
       c[x][y]=cap;
       v[x].push_back({y,cost});
       v[y].push_back({x,-cost});
   }
}
int Dijkstra()
{
    for(int i=1;i<=n;i++)
    {
        dist[i]=INT_MAX;
        tata[i]=-1;
        incoada[i]=0;
    }
    dist[s]=0; tata[s]=0;
    q.push(s);
    while(!q.empty())
    {
        int nod=q.top(); q.pop(); incoada[nod]=0;
        for(int j=0;j<v[nod].size();j++)
        {
            int vecin=v[nod][j].first;
            int cost=v[nod][j].second;
            if(c[nod][vecin]>0 && dist[vecin]>dist[nod]+cost)
            {
                 dist[vecin]=dist[nod]+cost;
                 tata[vecin]=nod;
                 if(!incoada[vecin])
                 {
                     incoada[vecin]=1;
                     q.push(vecin);
                 }
            }
        }
    }
    if(dist[d]==INT_MAX)
        return 0;
    return 1;
}
int main()
{
    citire();
    while(Dijkstra())
    {
        int vec=d; int flux=INT_MAX;
        while(vec!=s)
        {
            int vv=tata[vec];
            if(flux>c[vv][vec])
                flux=c[vv][vec];
            vec=vv;
        }
           vec=d;
        while(vec!=s)
        {
            int vv=tata[vec];
            c[vv][vec]-=flux;
            c[vec][vv]+=flux;
            vec=vv;
        }
       k=k+dist[d]*flux;

    }
    out<<k;
    return 0;
}