#pragma GCC optimize ("O3")
#include <bits/stdc++.h>

const int oo=2*(1e6);

using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

int n,m,S,D,i,j,fluxmax,C[360][360],cap[360][360],dist[360];
vector<int> v[360];

bool djikstra()
{

}

void bellman()
{
    queue<int> Q;
    bitset<360> in;
    for(i=1; i<=n; i++)
        dist[i]=oo,in[i]=0;
    dist[S]=0;
    in[S]=1;
    Q.push(S);
    while(Q.size())
    {
        int x=Q.front();
        Q.pop();
        in[x]=0;
        for(auto it:v[x])
            if(cap[x][it])
                if(dist[it]>dist[x]+C[x][it])
                {
                    dist[it]=dist[x]+C[x][it];
                    if(!in[it])
                    {
                        in[it]=1;
                        Q.push(it);
                    }
                }
    }
    return ;
}

int main()
{
    f>>n>>m>>S>>D;
    for(i=1; i<=m; i++)
    {
        int x,y,c,z;
        f>>x>>y>>c>>z;
        cap[x][y]=c;
        C[x][y]=z;
        C[y][x]=-z;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    bellman();
//    for(i=1;i<=n;i++)
//        cout<<dist[i]<<' ';cout<<'\n';
    for(;;)
    {
        priority_queue<pair<int,int> > Q;
        int d[360],real_d[360],tata[360];
        for(i=1; i<=n; i++)
            d[i]=real_d[i]=oo,tata[i]=0;
        d[S]=real_d[S]=0;
        Q.push({0,S});
        while(Q.size())
        {
            int x=Q.top().second,
                cost=Q.top().first;
            Q.pop();
            if(d[x]<cost)
                continue;
            for(auto it:v[x])
                if(cap[x][it])
                {
                    int new_d=d[x]+C[x][it]+dist[it]-dist[x];
                    if(new_d<d[it])
                    {
                        d[it]=new_d;
                        real_d[it]=real_d[x]+C[x][it];
                        tata[it]=x;
                        Q.push({d[it],it});
                    }
                }
        }
        for(i=1; i<=n; i++)
            dist[i]=real_d[i];
        if(dist[D]==oo)
            break;
//    for(i=1;i<=n;i++)
//        cout<<dist[i]<<' ';cout<<'\n';
        int x=D,flux=oo;
        while(tata[x]!=0)
        {
            flux=min(flux,cap[tata[x]][x]);
            x=tata[x];
        }
        x=D;
        //cout<<flux<<'\n';
        while(tata[x]!=0)
        {
            cap[tata[x]][x]-=flux;
            cap[x][tata[x]]+=flux;
            x=tata[x];
        }
        fluxmax+=flux*dist[D];
    }
    g<<fluxmax;
    return 0;
}