#include <fstream>
#include <vector>
#include <cstring>
#define Nmax 351
#define inf 1e9
#define pb push_back
using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

int n,m,S,D,x,y,ant[Nmax],fw[Nmax][Nmax],c[Nmax][Nmax],mn[Nmax];
vector<int> V[Nmax],C;
bool inQ[Nmax],ok;

bool bfs()
{
    C.clear();
    C.pb(S);

    ok = 0;

    memset(inQ,0,sizeof(inQ));
    inQ[S] = 1;
    inQ[D] = 1;

    memset(mn,0x3f,sizeof(mn));
    for (int i=0;i<C.size();i++)
    {
        int now = C[i];
        inQ[i] = 0;
        for (int j=0;j<V[now].size();j++)
        {
            if (fw[now][V[now][j]]!=0)
            {
                if (mn[V[now][j]]>mn[now] + c[now][V[now][j]])
                {
                    ant[V[now][j]] = now;
                    mn[V[now][j]] = mn[now] + c[now][V[now][j]];
                    if (V[now][j] == D)
                        ok = 1;
                    if (!inQ[V[now][j]])
                    {
                        C.pb(V[now][j]);
                        inQ[V[now][j]] = 1;
                    }
                }
            }
        }
    }
    return ok;
}

int main()
{
    f>>n>>m>>S>>D;
    for (int i=1;i<=m;i++)
    {
        f>>x>>y;
        f>>fw[x][y];
        f>>c[x][y];
        c[y][x] = -c[x][y];
        V[x].pb(y);
        V[y].pb(x);
    }

    int rez = 0;
    while (bfs())
    {
        int s = 0,nod = D,mx = inf;
        while (nod!=S)
        {
            mx = min(mx,fw[ant[nod]][nod]);
            s+=c[ant[nod]][nod];
            nod = ant[nod];
        }
        rez += s * mx;
        nod = D;
        while (nod!=S)
        {
            fw[ant[nod]][nod]-=mx;
            fw[nod][ant[nod]]+=mx;
            nod = ant[nod];
        }
    }
    g<<rez;
    return 0;
}