#include <bits/stdc++.h>

using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
const int Nmax=355;
int cost[Nmax][Nmax],C[Nmax][Nmax],dist[Nmax],tata[Nmax],n,m,s,d;
vector<int>G[Nmax];
queue<int>Q;
vector<int>::iterator it;
bitset<Nmax>viz;
const int inf=0x3f3f3f3f;
long long costflux;
bool bellmanford()
{
    memset(dist,inf,sizeof(dist));
    dist[s]=0;
    viz[s]=1;
    Q.push(s);
    while(Q.size())
    {
        int nod=Q.front();
        Q.pop();
        viz[nod]=0;
        for(it=G[nod].begin();it!=G[nod].end();it++)
        {
            if(C[nod][*it] && dist[*it]>dist[nod]+cost[nod][*it])
            {
                dist[*it]=dist[nod]+cost[nod][*it];
                tata[*it]=nod;
                if(viz[*it]==0)
                {
                    viz[*it]=1;
                    Q.push(*it);
                }
            }
        }
    }
    if(dist[d]==inf) return 0;
    return 1;
}
int main()
{
    int x,y,c,z,fmin,i;
    fin>>n>>m>>s>>d;
    while(m--)
    {
        fin>>x>>y>>c>>z;
        G[x].push_back(y);
        G[y].push_back(x);
        C[x][y]=c;
        cost[x][y]=z;
        cost[y][x]=-z;
    }
    while(bellmanford())
    {
        fmin=inf;
        for(i=d;i!=s;i=tata[i])
        {
            fmin=min(fmin,C[tata[i]][i]);
        }
        for(i=d;i!=s;i=tata[i])
        {
            C[tata[i]][i]-=fmin;
            C[i][tata[i]]+=fmin;
        }
        costflux+=dist[d]*fmin;
    }
    fout<<costflux;
}