#include <cstdio>
#include <queue>
#include <vector>
#include <algorithm>
#define N 355
#define oo 1<<30
using namespace std;
vector<int>v[N];
deque<int> Q;
priority_queue<pair<int,int> >q;
int n,m,s,d,CD,x,y,C[N][N],D[N][N],FL[N][N],c[N],tata[N],viz[N],i,X,sol,ok;
int bellman()
{
    Q.push_back(s);
    for(i=1;i<=n;i++)
    {
        c[i]=oo;
        tata[i]=0;
    }
    c[s]=0;
    while(Q.size())
    {
        X=Q.front();
        for(vector<int>::iterator it=v[X].begin();it!=v[X].end();it++)
            if(C[X][*it]-FL[X][*it]>0&&c[*it]>c[X]+D[X][*it])
            {
                c[*it]=c[X]+D[X][*it];
                tata[*it]=X;
                {Q.push_back(*it);viz[*it]=1;}
            }
        Q.pop_front();
    }
    if(c[d]!=oo)
    {
        ok=1;
        int fl=oo;
        for(x=tata[d],y=d;y!=s;x=tata[x],y=tata[y])
            fl=min(fl,C[x][y]-FL[x][y]);
        for(x=tata[d],y=d;y!=s;x=tata[x],y=tata[y])
        {
            FL[x][y]+=fl;
            FL[y][x]-=fl;
        }
        return fl*c[d];
    }
    return 0;
}
int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
    scanf("%d%d%d%d",&n,&m,&s,&d);
    for(;m;m--)
    {
        scanf("%d%d",&x,&y);
        scanf("%d%d",&C[x][y],&D[x][y]);
        v[x].push_back(y);
        v[y].push_back(x);
        D[y][x]=-D[x][y];
    }
    ok=1;
    while(ok)
    {
        ok=0;
        sol+=bellman();
    }
    printf("%d\n",sol);
    return 0;
}