#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define INF numeric_limits<int>::max()
#define int64 long long
using namespace std;
ifstream in("fmcm.in");
ofstream out("fmcm.out");
vector< vector<int> > adj;
int n,m,cost[1024][1024],flow[1024][1024],cap[1024][1024],pre[1024],S,D,dist[1024];
bool use[1024];
queue<int> Q;
bool bellman()
{
    for(int i=1;i<=n;i++)
    {
        dist[i]=INF;
        pre[i]=0;
        use[i]=false;
    }
    Q.push(S);
    dist[S]=0;
    pre[S]=S;
    while(!Q.empty())
    {
        int x=Q.front();
        Q.pop();
        use[x]=false;
        for(auto it: adj[x])
        if(dist[it] > dist[x] + cost[x][it] && cap[x][it]>flow[x][it])
        {
            dist[it]=dist[x] + cost[x][it];
            pre[it]=x;
            if(use[it]==false)
            {
                use[it]=true;
                Q.push(it);
            }
        }
    }
    return (pre[D]!=0);
}
int main()
{
    in>>n>>m>>S>>D;
    adj=vector< vector<int> > (n+1);
    for(;m;m--)
    {
        int x,y,z,w;
        in>>x>>y>>z>>w;
        adj[x].pb(y);
        adj[y].pb(x);
        cap[x][y]=z;
        cost[x][y]=w;
        cost[y][x]=-w;
    }
    int maxflow=0,totalCost=0;
    while(bellman()==true)
    {
        int mx=INF;
        for(int x=D;x!=pre[x];x=pre[x])
            mx=min(mx,cap[pre[x]][x]-flow[pre[x]][x]);
        for(int x=D;x!=pre[x];x=pre[x])
        {
            flow[pre[x]][x]+=mx;
            flow[x][pre[x]]-=mx;
            totalCost+=cost[pre[x]][x]*mx;
        }
        maxflow+=mx;
    }
    out<<totalCost<<'\n';
    return 0;
}