#include <bits/stdc++.h>

using namespace std;
const int Nmax=355;
int cost[Nmax][Nmax],C[Nmax][Nmax],dist[Nmax],tata[Nmax],n,m,s,d,real_dist[Nmax],dij_dist[Nmax];
vector<int>G[Nmax];
queue<int>Q;
vector<int>::iterator it;
bitset<Nmax>viz;
const int inf=0x3f3f3f3f;
int costflux;
priority_queue <pair <int, int>, vector <pair <int, int> >, greater<pair <int, int> > > Heap;
bool bellmanford()
{
    memset(dist,inf,sizeof(dist));
    dist[s]=0;
    viz[s]=1;
    Q.push(s);
    while(Q.size())
    {
        int nod=Q.front();
        Q.pop();
        viz[nod]=0;
        for(it=G[nod].begin();it!=G[nod].end();it++)
        {
            if(C[nod][*it] && dist[*it]>dist[nod]+cost[nod][*it])
            {
                dist[*it]=dist[nod]+cost[nod][*it];
                if(viz[*it]==0)
                {
                    viz[*it]=1;
                    Q.push(*it);
                }
            }
        }
    }
    if(dist[d]==inf) return 0;
    return 1;
}
bool dijkstra()
{
    memset(dij_dist,inf,sizeof(dij_dist));
    dij_dist[s]=real_dist[s]=0;
    Heap.push(make_pair(dij_dist[s],s));
    while(Heap.size())
    {
        int nod=Heap.top().second,cst=Heap.top().first;
        Heap.pop();
        if(dij_dist[nod]!=cst) continue;
        for(it=G[nod].begin();it!=G[nod].end();it++)
        {
            if(C[nod][*it])
            {
                int step=dij_dist[nod]+cost[nod][*it]+dist[nod]-dist[*it];
                if(step<dij_dist[*it])
                {
                    real_dist[*it]=real_dist[nod]+cost[nod][*it];
                    dij_dist[*it]=step;
                    tata[*it]=nod;
                    Heap.push(make_pair(dij_dist[*it],*it));
                }
            }
        }
    }
     memcpy(dist,real_dist,sizeof(dist));
    if(dij_dist[d]==inf) return 0;
        int fmin=inf,i;
        for(i=d;i!=s;i=tata[i])
        {
            fmin=min(fmin,C[tata[i]][i]);
        }
        for(i=d;i!=s;i=tata[i])
        {
            C[tata[i]][i]-=fmin;
            C[i][tata[i]]+=fmin;
        }
        costflux+=real_dist[d]*fmin;
        return 1;
}
int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
    int x,y,c,z,fmin,i;
    //fin>>n>>m>>s>>d;
    scanf("%d%d%d%d",&n,&m,&s,&d);
    while(m--)
    {
        //fin>>x>>y>>c>>z;
        scanf("%d%d%d%d",&x,&y,&c,&z);
        G[x].push_back(y);
        G[y].push_back(x);
        C[x][y]=c;
        cost[x][y]=z;
        cost[y][x]=-z;
    }
    bellmanford();
    while(dijkstra());
    printf("%d",costflux);
}