#include<fstream>
#include<vector>
#include<bitset>
#include<deque>
#define inf 100000000
using namespace std;
vector <int> L[353];
bitset <353> v;
deque <int> q;
int T[353], x, y, z, c, n, m, s, d, i, nod, minim, cost, C[353][353], F[353][353], Z[353][353], D[353], vecin;
int bf(int s)
{
    for(int i=1; i<=n; i++)
        D[i]=inf;
    D[s]=0;
    v.reset();
    v[s]=1;
    q.clear();
    q.push_back(s);
    while(!q.empty())
    {
        nod=*q.begin();
        for(int i=0; i<L[nod].size(); i++)
        {
            vecin=L[nod][i];
            if(C[nod][vecin]-F[nod][vecin]>0 && D[vecin]>D[nod]+Z[nod][vecin])
            {
                D[vecin]=D[nod]+Z[nod][vecin];
                T[vecin]=nod;
                if(v[vecin]==0)
                {
                    q.push_back(vecin);
                    v[vecin]=1;
                }
            }
        }
        q.pop_front();
        v[nod]=0;
    }
    if(D[d]!=inf)
        return 1;
    return 0;
}
ifstream in("fmcm.in");
ofstream out("fmcm.out");
int main()
{
    in>>n>>m>>s>>d;
    for(i=1; i<=m; i++)
    {
        in>>x>>y>>c>>z;
        L[x].push_back(y);
        C[x][y]=c;
        Z[x][y]=z;
        L[y].push_back(x);
        Z[y][x]=-z;
    }
    while(bf(s))
    {
        //for(i=0; i<L[d].size(); i++)
        //{
            minim=C[T[d]][d]-F[T[d]][d];
            for(nod=T[d]; nod!=s && minim!=0; nod=T[nod])
            {
                minim=min(minim, C[T[nod]][nod]-F[T[nod]][nod]);
            }
            if(minim!=0)
            {
                F[T[d]][d]+=minim;
                F[d][T[d]]-=minim;
                cost+=minim*Z[T[d]][d];
                for(nod=T[d]; nod!=s; nod=T[nod])
                {
                    cost+=minim*Z[T[nod]][nod];
                    F[T[nod]][nod]+=minim;
                    F[nod][T[nod]]-=minim;
                }
            }
        //}
    }
    out<<cost;
    return 0;
}