#include<cstdio>
#include<vector>
#include<deque>
#include<bitset>
#include<algorithm>
using namespace std;
const int nmax = 355;
const int inf = (1LL<<31)-1;
int i,n,m,s,d,x,y,z,t,ctotal,add,cap[nmax][nmax],cost[nmax][nmax],flow[nmax][nmax],dist[nmax],f[nmax];
vector<int> v[nmax];
deque<int> q;
bitset<nmax> inq;
bool bf()
{
    for(i=1;i<=n;i++) dist[i]=inf;
    dist[s]=0; f[s]=s; inq[s]=1; q.push_back(s);
    while(!q.empty())
    {
        x=q.front(); q.pop_front(); inq[x]=0;
        for(vector<int>::iterator it=v[x].begin();it!=v[x].end();it++)
            if(dist[x]+cost[x][*it]<dist[*it] && flow[x][*it]<cap[x][*it])
            {
                dist[*it]=dist[x]+cost[x][*it];
                f[*it]=x;
                if(!inq[*it])
                {
                    inq[*it]=1;
                    q.push_back(*it);
                }
            }
    }
    return dist[d]!=inf;
}
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",&x,&y,&z,&t);
	    v[x].push_back(y);
	    v[y].push_back(x);
	    cap[x][y]=z;
	    cost[x][y]=t; cost[y][x]=-t;
	}
	while(bf())
	{
	    add=inf;
	    for(x=d;x!=f[x];x=f[x])
            add=min(add,cap[f[x]][x]-flow[f[x]][x]);
        for(x=d;x!=f[x];x=f[x])
        {
            flow[f[x]][x]+=add;
            flow[x][f[x]]-=add;
        }
        ctotal+=dist[d]*add;
	}
	printf("%d\n",ctotal);
	return 0;
}