#include <bits/stdc++.h>
#define mp make_pair
#define f first
#define s second
#define nmax 460
using namespace std;

ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

typedef pair<int,int> per ;

int n,m,A,B,C,D,S,DE,i,ans,fc,j,cost_total;

int t[nmax];

int c[nmax][nmax],f[nmax][nmax],ct[nmax][nmax],d[nmax];

vector < int > v[nmax];

priority_queue < per, vector<per>, greater<per> > pq;

bool dijkstra()
{
    int nod=0;
    memset(d,1e6,sizeof(d));
    memset(t,0,sizeof(t));
    pq.push(mp(0,S));
    t[S]=-1;
    d[S]=0;
    while(!pq.empty())
    {
        nod=pq.top().s;pq.pop();
        for(auto it:v[nod])
        {
            if(t[it]||c[nod][it]==f[nod][it])continue;
            if(d[nod]+ct[nod][it]<d[it])
            {
                d[it]=d[nod]+ct[nod][it];
                t[it]=nod;
                pq.push(mp(d[it],it));
            }
        }
    }
    if(t[DE])return true;
    return false;
}

int main()
{
    fin>>n>>m>>S>>DE;
    for(i=1; i<=m; i++)
    {
        fin>>A>>B>>C>>D;
        v[A].push_back(B);
        v[B].push_back(A);
        c[A][B]=C;
        ct[A][B]=D;
        ct[B][A]=-D;

    }
    while(dijkstra())
    {
        for(auto it:v[DE])
        {
            if(!t[it]||c[it][DE]==f[it][DE]||!c[it][DE])continue;
            fc=c[it][DE]-f[it][DE];
            cost_total=0;
            for(j=DE; j!=S; j=t[j])
            {
                fc=min(fc,c[t[j]][j]-f[t[j]][j]);
            }
            if(!fc)continue;
            for(j=DE; j!=S; j=t[j])
            {
                f[t[j]][j]+=fc;
                f[j][t[j]]-=fc;
                cost_total+=ct[t[j]][j];
            }
            ans+=cost_total*fc;
        }
    }
    fout<<ans;
    return 0;
}