#include<cstdio>
#include<vector>
#include<deque>
#define M 25010
#define N 351
using namespace std;
int n,m,s,d,i,j,k,cp,cs,cap[N][N],flow[N][N],q[N],dad[N],P[N],price[N][N],PRICE,bellman(),oo=2000000000;
vector<int> v[N];
deque<int> Q;
void upd();
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%d%d",&i,&j,&cp,&cs);
        cap[i][j]=cp;
        price[i][j]=cs;
        price[j][i]=-cs;
        v[i].push_back(j);
        v[j].push_back(i);
    }
    for(;bellman();)
        upd();
    printf("%d\n",PRICE);
    return 0;
}
int bellman()
{
    for(i=1;i<=n;i++)P[i]=oo;P[s]=0;dad[s]=s;dad[d]=0;
    Q.resize(0);
    Q.push_back(s);q[s]=1;
    for(;Q.size();)
    {
        m=Q.front();
        for(vector<int>:: iterator it=v[m].begin();it!=v[m].end();it++)
            if(cap[m][*it]-flow[m][*it]>0&&P[*it]>P[m]+price[m][*it])
            {
                if(!q[*it]){q[*it]=1;Q.push_back(*it);}
                dad[*it]=m;
                P[*it]=P[m]+price[m][*it];
            }
        Q.pop_front();q[m]=0;
    }
    if(!dad[d])return 0;
    return 1;
}
void upd()
{
    for(m=oo,i=d,j=dad[d];i-j;i=dad[i],j=dad[j])
          m=min(m,cap[j][i]-flow[j][i]);
    PRICE+=m*P[d];
    for(i=d,j=dad[d];i-j;i=dad[i],j=dad[j])
    {
        flow[i][j]-=m;
        flow[j][i]+=m;
    }
}