#include <bits/stdc++.h>

using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

int n,maxflow,tata[500],dist[500],min_dist[500],new_dist[500],cost[500][500],c[500][500],flux[500][500];
vector <int> v[500];
priority_queue < pair <int,int> , vector <pair <int,int> > , greater < pair < int ,int > > > q;

void Bellman_Ford(int nod_start)
{
    int i,nod;

    for(i=1;i<=n;i++)dist[i]=INT_MAX/2;
    dist[nod_start]=0;
    q.push({0,nod_start});

    while(!q.empty())
    {
        nod=q.top().second;
        if(q.top().first > dist[nod]){q.pop();continue;}
        else q.pop();

        for(i=0;i<v[nod].size();i++)
        {
            int vecin=v[nod][i];
            if(dist[vecin]>dist[nod]+cost[nod][vecin] && flux[nod][vecin]<c[nod][vecin])
            {
                dist[vecin]=dist[nod]+cost[nod][vecin];
                q.push({dist[vecin],vecin});
            }
        }
    }
}

int Dijkstra(int nod_start,int nod_final)
{
    int i,nod,flux_min;

    for(i=1;i<=n;i++)min_dist[i]=INT_MAX/2,tata[i]=0;
    min_dist[nod_start]=0;new_dist[nod_start]=0;
    q.push({0,nod_start});

    while(!q.empty())
    {
        nod=q.top().second;
        if(q.top().first > min_dist[nod]){q.pop();continue;}
        else q.pop();

        for(i=0;i<v[nod].size();i++)
        {
            int vecin=v[nod][i];
            int dist_intre=cost[nod][vecin]+dist[nod]-dist[vecin];
            if(flux[nod][vecin] < c[nod][vecin] && min_dist[vecin]>min_dist[nod]+dist_intre)
            {
                min_dist[vecin]=min_dist[nod]+dist_intre;
                q.push({min_dist[vecin],vecin});
                new_dist[vecin]=new_dist[nod]+cost[nod][vecin];
                tata[vecin]=nod;
            }
        }
    }

    if(min_dist[nod_final]==INT_MAX/2)return 0;


    nod=nod_final;
    flux_min=INT_MAX;
    while(tata[nod]!=0)
    {
        flux_min=min(flux_min,c[tata[nod]][nod]-flux[tata[nod]][nod]);
        nod=tata[nod];
    }

    maxflow+=flux_min*new_dist[nod_final];

    nod=nod_final;
    while(tata[nod]!=0)
    {
        flux[tata[nod]][nod]+=flux_min;
        flux[nod][tata[nod]]-=flux_min;
        nod=tata[nod];
    }

    for(i=1;i<=n;i++)dist[i]=new_dist[i];

    return 1;
}

int i,m,S,x,y,D,flux_cant,mch_cost;
int main()
{
    f>>n>>m>>S>>D;
    for(i=1;i<=m;i++)
    {
        f>>x>>y>>flux_cant>>mch_cost;
        v[x].push_back(y);
        v[y].push_back(x);
        c[x][y]=flux_cant;
        cost[x][y]=mch_cost;cost[y][x]=-mch_cost;
    }

    Bellman_Ford(S);
    while(Dijkstra(S,D));

    g<<maxflow;
    return 0;
}