#include <bits/stdc++.h>
#define ll long long

using namespace std;

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

const ll inf = 1e18 + 5;

vector <vector<int>> v, cost, cap;
vector <ll> d, old;
vector <int> tt;

bool dijkstra(int n, int s, int dest){
    vector <bool> vis(n + 1);
    vector <ll> newD(n + 1);

    vis[s] = true;
    d[s] = 0;

    priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> q;
    q.push(make_pair(d[s], s));

    while(!q.empty()){
        int x = q.top().second, c = q.top().first;
        q.pop();

        if(d[x] < c)
            continue;

        for(auto y: v[x])
            if(cap[x][y]){
                int newDist = d[x] + cost[x][y] + old[x] - old[y];
                if(newDist < d[y]){
                    d[y] = newDist;
                    newD[y] = newD[x] + cost[x][y];
                    q.push(make_pair(d[y], y));
                    tt[y] = x;
                    vis[y] = true;
                }
            }
    }

    old = newD;
    return vis[dest];
}

int main()
{
    int n, m, s, dest;
    fin >> n >> m >> s>> dest;

    cost.resize(n + 1, vector<int>(n + 1));
    cap.resize(n + 1, vector<int>(n + 1));
    v.resize(n + 1);
    d.resize(n + 1, inf);
    old.resize(n + 1);
    tt.resize(n + 1, -1);

    for(int i = 1; i <= m; i++){
        int x, y, c, z;
        fin >> x >> y >> c >>z;
        cost[x][y] = z;
        cost[y][x] = -z;
        cap[x][y] = c;
        v[x].push_back(y);
        v[y].push_back(x);
    }

    ll flow = 0, flowCost = 0;
    while(dijkstra(n, s, dest)){
        ll val = inf;

        for(int x = dest; x != s; x = tt[x])
            val = min(val, (ll)cap[tt[x]][x]);

        for(int x = dest; x != s; x = tt[x]){
            cap[tt[x]][x] -= val;
            cap[x][tt[x]] += val;
        }

        flow += val;
        flowCost += val * old[dest];
        fill(tt.begin(), tt.end(), -1);
        fill(d.begin(), d.end(), inf);
    }

    fout << flowCost;

    return 0;
}