#include <fstream>
#include <vector>
#include <queue>
#define INF 1<<30

using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
int n,m,i,nood,s[400],tt[400],start,finish,flux,dist[400],nod,x,y,cap,cost,Min;
struct coce{int cost,flux;} a[400][400];

vector<int> v[400];
queue<int> cd;

void reset()
{
    for (int i=1;i<=n;i++)
        s[i]=0,dist[i]=INF,tt[i]=0;
}

int bellman()
{
    cd.push(start);
    dist[start]=0;
    while (cd.empty() == false)
    {
        nod=cd.front();
        cd.pop();
        s[nod]=0;
        for (vector<int>::iterator it = v[nod].begin(); it != v[nod].end(); it ++)
        {
            if (dist[nod]+a[nod][*it].cost < dist[*it] && a[nod][*it].flux)
            {
                dist[*it] = dist[nod]+a[nod][*it].cost;
                tt[*it]=nod;
                if (s[*it]==0)
                {
                    s[*it]=1;
                    cd.push(*it);
                }
            }
        }
    }
    if (tt[finish])
        return 1;
    else
        return 0;
}
int main()
{
    fin>>n>>m>>start>>finish;
    for (i=1;i<=m;i++)
    {
        fin>>x>>y>>cap>>cost;
        v[x].push_back(y);
        v[y].push_back(x);
        a[x][y].flux=cap;
        a[x][y].cost=cost;
        a[y][x].cost=-cost;
    }
    reset();
    while (bellman())
    {
        nod=finish;
        Min=a[tt[nod]][nod].flux;
        while (nod!=start)
        {
            Min=min(Min,a[tt[nod]][nod].flux);
            nod=tt[nod];
        }
        nod=finish;
        a[nod][tt[nod]].flux-=Min;
        while (nod!=start)
        {
            a[tt[nod]][nod].flux-=Min;
            a[nod][tt[nod]].flux+=Min;
            flux+=Min*a[tt[nod]][nod].cost;
            nod=tt[nod];
        }
        reset();
    }
    fout<<flux;
    return 0;
}