#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <queue>
using namespace std;
ifstream f("fmcm.in");
ofstream g("fmcm.out");
const int NMAX = 355;
int C[NMAX][NMAX],F[NMAX][NMAX],cost[NMAX][NMAX],flux,constanta[NMAX];
vector <int> G[NMAX],T;
int n,m,s,d;
int BF(int start)
{
    T = vector<int>(n+1,0);
    T[start] = -1;
    queue <int> q;
    q.push(start);
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        for(int x : G[u])
            if(!T[x] && C[u][x]>F[u][x])
        {
            T[x]=u;
            q.push(x);
        }
    }
    return T[d]!=0;
}
const int INF = 1e8;
void bellman(int start, int fin)
{
    int i, crt, urm;
    for(i = 1; i<=n; i++)
        constanta[i] = INF;
     queue<int>coada;
    constanta[start] = 0;
    coada.push(start);

    while(!coada.empty())
    {
        crt = coada.front();
        coada.pop();
        for(int urm : G[crt])
         if(constanta[urm] > constanta[crt] + cost[crt][urm] && C[crt][urm] > F[crt][urm] )
            {
                constanta[urm] = constanta[crt] + cost[crt][urm];
                coada.push(urm);
            }
    }
}
int main()
{
    f>>n>>m>>s>>d;
    while(m--)
    {
        int a,b,c,d;
        f>>a>>b>>c>>d;
        G[a].push_back(b);
        G[b].push_back(a);
        C[a][b]=c;
        cost[a][b]=d;
        cost[b][a]=-d;
    }
    f.close();
    bellman(s,d);
    while(BF(s))
    {
        int r=INF;
        for(int j=d;j!=s;j=T[j])
                r= min(r,C[T[j]][j]-F[T[j]][j]);
        int cst = 0;
            for(int j=d;j!=s;j=T[j])
                F[T[j]][j]+=r,F[j][T[j]]-=r,cst+=cost[T[j]][j];
        flux+=r*cst;
    }
    g<<flux;
    g.close();
}