#include<fstream>
#include<vector>
#include<cstring>
#include<queue>
#define inf 0x7f7f7f7f
using namespace std;
vector<int> L[352];
queue<int> q;
bool u[352];
int T[352], D[352], C[352][352], F[352][352], Z[352][352], s, n, nod, vecin, cost, i, m, d, minim, x, y, z, c;
int bellmanford()
{
    memset(D, 127, sizeof(D));
    D[s]=0;
    memset(u, 0, sizeof(u));
    u[s]=1;
    q.push(s);
    while(!q.empty())
    {
        nod=q.front();
        for(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(u[vecin]==0)
                {
                    q.push(vecin);
                    u[vecin]=1;
                }
            }
        }
        u[nod]=0;
        q.pop();
    }
    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);
        L[y].push_back(x);
        C[x][y]=c;
        Z[x][y]=z;
        Z[y][x]=-z;
    }
    while(bellmanford())
    {
        minim=C[T[d]][d]-F[T[d]][d];
        for(nod=T[d]; T[nod]!=0 && 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]; T[nod]!=0; nod=T[nod])
            {
                F[T[nod]][nod]+=minim;
                F[nod][T[nod]]-=minim;
                cost+=minim*Z[T[nod]][nod];
            }
        }
    }
    out<<cost;
    return 0;
}