#include<stdio.h>
#define INF 10000001
#define Nmx 350
#include<vector>
#include<queue>

using namespace std;

int C[Nmx][Nmx],Cst[Nmx][Nmx],prec[Nmx],F[Nmx][Nmx],viz[Nmx],cost[Nmx],n,m,s,d;
vector<int> G[Nmx];
struct cmp
{
    bool operator()(const int &a,const int &b) const
    {
        cost[a]<cost[b];
    }
};
priority_queue< int, vector<int> , cmp > Q;

void citire()
{
    scanf("%d%d%d%d",&n,&m,&s,&d);
    int x,y,c,z;
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d%d%d",&x,&y,&c,&z);
        G[x].push_back(y);
        G[y].push_back(x);
        C[x][y]=c;
        Cst[x][y]=z;
        Cst[y][x]=-z;
    }
}

int min(int a,int b)
{
    if(a<b)
        return a;
    return b;
}

int belmand()
{
    vector<int> ::iterator it;
    for(int i=1;i<=n;++i)
        cost[i]=INF;
    cost[s]=0;
    Q.push(s);
    while(!Q.empty())
    {
        int nod=Q.top();
        Q.pop();
        viz[nod]=0;
        for(it=G[nod].begin();it!=G[nod].end();++it)
            if(cost[*it]>cost[nod]+Cst[nod][*it]&&C[nod][*it]-F[nod][*it]>0)
            {
                cost[*it]=cost[nod]+Cst[nod][*it];
                prec[*it]=nod;
                if(!viz[*it])
                {
                    viz[*it]=1;
                    Q.push(*it);
                }
            }
    }
    if(cost[d]<INF)
        return 1;
    return 0;
}

void solve()
{
    int sol=0;
    while(belmand())
    {
        int Vmin=INF;
        for(int i=d;i!=s;i=prec[i])
            Vmin=min(Vmin,C[prec[i]][i]-F[prec[i]][i]);
        for(int i=d;i!=s;i=prec[i])
        {
            F[prec[i]][i]+=Vmin;
            F[i][prec[i]]-=Vmin;
        }
        sol+=Vmin*cost[d];
    }
    printf("%d\n",sol);
}

int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
    citire();
    solve();
    return 0;
}