#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <string.h>

using namespace std;
#define MAX 400
#define INF 1000000000
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

typedef vector<int>::iterator iter;

int Cap[MAX][MAX], Cost[MAX][MAX], Flow[MAX][MAX];
vector<int> G[MAX];
queue<int> Q;
int dist[MAX], p[MAX];
int totalFlow = 0;
int n;
bool bfs(int s, int d){
    int i;
    for(i = 1 ; i <= n ; i++)
        dist[i] = INF;
    memset(p, 0, sizeof(p));
    dist[s] = 0;
    Q.push(s);

    while(Q.size()) {
        int node = Q.front();
        Q.pop();
//        cout << node << "\n";
        for(iter it = G[node].begin() ; it != G[node].end() ; it++) {
//            cout << *it  << "\n";
//            cout << dist[node] << " " << Cost[node][*it] << " " << dist[*it] << "\n";
            if(dist[node] + Cost[node][*it] < dist[*it] && Cap[node][*it] > Flow[node][*it]) {
                dist[*it] = dist[node] + Cost[node][*it];
                p[*it] = node;
                if(*it == d)
                    break;
                Q.push(*it);

            }
        }
    }
    if(dist[d] == INF)
        return 0;


    int flux = INF;

    for(int i = d ; i != s ; i = p[i]) {
        flux = min(flux, Cap[p[i]][i] - Flow[p[i]][i]);
    }
    for(int i = d ; i != s ; i = p[i]) {
        Flow[p[i]][i] += flux;
        Flow[i][p[i]] -= flux;
    }
    totalFlow += flux * dist[d];

    return 1;
}

int main(){
    int m, i, j, s, d;
    fin >> n >> m >> s >> d;

    while(m--){
        int x, y, c, z;
        fin >> x >> y >> c >> z;
        G[x].push_back(y);
        G[y].push_back(x);
//        cout << x << " " << y << "\n";
        Cap[x][y] += c;
        Cost[x][y] += z;
        Cost[y][x] -= z;
        Flow[x][y] = 0;
    }

    while(bfs(s, d)) {

    }
    cout << totalFlow << "\n";
}