#include <bits/stdc++.h>

using namespace std;
int n,m,x,y,s,d,ans;
int cap[355][355],cst[355][355],cost_min[355],from[355];
bool in_queue[355];
vector<int>nod[355];
int main()
{
    ifstream fin("fmcm.in");
    ofstream fout("fmcm.out");
    fin>>n>>m>>s>>d;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        fin>>cap[x][y]>>cst[x][y];
        cst[y][x]=-cst[x][y];
        nod[x].push_back(y);
        nod[y].push_back(x);
    }
    while(true)
    {
        for(int i=1;i<=n;i++)
            cost_min[i]=INT_MAX;
        cost_min[s]=0;
        queue<int>q;
        q.push(s);
        while(!q.empty())
        {
            int pos=q.front();
            q.pop();
            in_queue[pos]=false;
            for(int i=0;i<nod[pos].size();i++)
                if(cap[pos][nod[pos][i]] && cost_min[pos]+cst[pos][nod[pos][i]]<cost_min[nod[pos][i]])
                {
                    cost_min[nod[pos][i]]=cost_min[pos]+cst[pos][nod[pos][i]];
                    from[nod[pos][i]]=pos;
                    if(!in_queue[nod[pos][i]])
                    {
                        q.push(nod[pos][i]);
                        in_queue[nod[pos][i]]=true;
                    }
                }
        }
        if(cost_min[d]==INT_MAX)
            break;
        int flow=INT_MAX;
        int pos=d;
        while(pos!=s)
        {
            flow=min(flow,cap[from[pos]][pos]);
            pos=from[pos];
        }
        pos=d;
        while(pos!=s)
        {
            cap[from[pos]][pos]-=flow;
            cap[pos][from[pos]]+=flow;
            pos=from[pos];
        }
        ans+=flow*cost_min[d];
    }
    fout<<ans;
    return 0;
}