using namespace std;
#include<iostream>
#include<fstream>
#include<vector>
#include<queue>
#define oo 0x3f3f3f3f
#define nmax 1005
#define pb push_back
ofstream fout("fmcm.out");
struct nod{
int lg,c;};
queue<int> q;
vector<nod> G[nmax];
int N,M,S,D;
int C[nmax][nmax],F[nmax][nmax];
int viz[nmax],isinq[nmax],dp[nmax],ante[nmax];
bool BFS()
{int i;
    for(i=0;i<=N;i++)
    {
        dp[i]=oo;
        viz[i]=0;
        isinq[i]=0;
    }
    q.push(S);
    viz[S]=1;
    dp[S]=0;
    isinq[S]=1;
    int u;
    vector<nod>::iterator it;
    while(!q.empty())
    {
        u=q.front();
        q.pop();
        isinq[u]=0;
       //cout<<u<<" ";

        for(it=G[u].begin();it<G[u].end();it++)
        {
            if(dp[it->lg]>dp[u]+it->c && C[u][it->lg]>F[u][it->lg])
            {
                dp[it->lg]=dp[u]+it->c;
                viz[it->lg]=1;
                ante[it->lg]=u;
                if(!isinq[it->lg])
                {
                    q.push(it->lg);
                    isinq[it->lg]=1;

                }
            }
        }

    }
    return viz[D];
}

void solve()
{int flow=0,fmin,i;
vector<int>::iterator it;
    for(;BFS();)
    {   //cout<<1;
        fmin=C[ante[D]][D]-F[ante[D]][D];
        for(i=ante[D];i!=S;i=ante[i])
        {
            fmin=min(fmin,C[ante[i]][i]-F[ante[i]][i]);

        }
        F[ante[D]][D]+=fmin;
        F[D][ante[D]]-=fmin;
        for(i=ante[D];i!=S;i=ante[i])
        {
            F[ante[i]][i]+=fmin;
            F[i][ante[i]]-=fmin;
        }
        //cout<<fmin<<" "<<dp[D]<<"\n";
        flow+=fmin*dp[D];
    }
    fout<<flow<<"\n";
}

void cit()
{
    ifstream fin("fmcm.in");

    fin>>N>>M>>S>>D;
    int i,x,y,z,c;
    for(i=1;i<=M;i++)
    {
        fin>>x>>y>>c>>z;
        G[x].pb((nod){y,z});
        G[y].pb((nod){x,-z});
        //cout<<x<<" "<<y<<"\n";
        C[x][y]+=c;

    }
    fin.close();
}


int main()
{

    cit();

    solve();

    fout.close();

    return 0;
}