#include <bits/stdc++.h>
using namespace std;
ifstream in("fmcm.in");
ofstream out("fmcm.out");
const int inf=2e9+7;
vector<int> vec[705];
int cap[705][705];
int cost[705][705];
bool inq[705];
int dist[705];
int prv[705];
queue<int> q;
int n,m,st,dr;
int x,y,z,t;
int main()
{
    in>>n>>m>>st>>dr;
    for(int i=1;i<=m;++i)
    {
        in>>x>>y>>z>>t;
        vec[x].push_back(y);
        vec[y].push_back(x);
        cap[x][y]=z;
        cap[y][x]=0;
        cost[x][y]=t;
        cost[y][x]=-t;
    }
    int flow=0,price=0;
    do
    {
        for(int i=1;i<=n;++i)
            dist[i]=inf,prv[i]=-1,inq[i]=false;
        dist[st]=0;
        prv[st]=0;
        q.push(st);
        inq[st]=true;
        while(!q.empty())
        {
            int x=q.front(); q.pop();
            inq[x]=false;
            for(int y:vec[x])
            if(dist[y]>dist[x]+cost[x][y] and cap[x][y]>0)
            {
                dist[y]=dist[x]+cost[x][y];
                prv[y]=x;
                if(!inq[y])
                    inq[y]=true,
                    q.push(y);
            }
        }
        if(prv[dr]!=-1)
        {
            int el=dr;
            int minim=inf;
            int addons=0;
            while(prv[el]>0)
                minim=min(minim,cap[prv[el]][el]),
                addons+=cost[prv[el]][el],
                el=prv[el];
            flow+=minim;
            price+=minim*addons;
            el=dr;
            while(prv[el]>0)
                cap[prv[el]][el]-=minim,
                cap[el][prv[el]]+=minim,
                el=prv[el];
        }
    }while(prv[dr]!=-1);
    //out<<flow<<' '<<price<<'\n';
    out<<price<<'\n';
    return 0;
}