#include <bits/stdc++.h>

#pragma optimize GCC ("Ofast")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

///#include <tryhardmode>
///#include <GODMODE::ON>

using namespace std;

#define cin fin
#define cout fout

ifstream fin ("fmcm.in");
ofstream fout ("fmcm.out");

const int INF=2e9;
const int NMAX=355;

vector<pair<int,int>>v[NMAX];

int t[NMAX];
int flux[NMAX][NMAX];
int dist[NMAX];
bool viz[NMAX];

int n,s,d;

int bellman()
{
    int i;
    for(i=1;i<=n;i++)
    {
        viz[i]=false;
        dist[i]=INF;
    }
    queue<int>q;
    q.push(s);
    viz[s]=true;
    dist[s]=0;
    while(!q.empty())
    {
        int p=q.front();
        q.pop();
        viz[p]=false;
        for(auto i:v[p])
        {
            if(dist[i.first]>dist[p]+i.second && flux[p][i.first]>0)
            {
                t[i.first]=p;
                dist[i.first]=dist[p]+i.second;
                if(!viz[i.first])
                {
                    viz[i.first]=true;
                    q.push(i.first);
                }
            }
        }
    }
    return dist[d];
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int m,i,j;
    long long kon=0;
    cin>>n>>m>>s>>d;
    for(i=1;i<=m;i++)
    {
        int x,y,cost,cap;
        cin>>x>>y>>cap>>cost;
        v[x].push_back(make_pair(y,cost));
        v[y].push_back(make_pair(x,-cost));
        flux[x][y]=cap;
    }
    while(true)
    {
        int suma=bellman();
        int mini=INF;
        int x;
        if(suma==INF)
            break;
        x=d;
        while(x!=s)
        {
            mini=min(mini,flux[t[x]][x]);
            x=t[x];
        }
        if(mini==0)
            continue;
        x=d;
        while(x!=s)
        {
            flux[x][t[x]]+=mini;
            flux[t[x]][x]-=mini;
            x=t[x];
        }
        kon+=mini*suma;
    }
    cout<<kon;
    return 0;
}