#include <iostream>
#include <fstream>
#include <queue>
#include <vector>
#include <algorithm>

using namespace std;

const char iname[] = "fmcm.in";
const char oname[] = "fmcm.out";

#define MAXN  355
#define Min(a, b)  ((a) < (b) ? (a) : (b))

vector <int> adj[MAXN];

int Cst[MAXN][MAXN], C[MAXN][MAXN], F[MAXN][MAXN], n, src, sink;

void read_in(void)
{
    ifstream in(iname);
    int cnt_edges, x, y, cap, cst;

    in >> n >> cnt_edges >> src >> sink;
    for (; cnt_edges > 0; -- cnt_edges) {
        in >> x >> y >> cap >> cst;
        Cst[x][y] = cst, Cst[y][x] = -cst;
        C[x][y]   = cap;
        adj[x].push_back(y), adj[y].push_back(x);
    }
    in.close();
}

int BF(void)
{
    const int infinity = int(1e9);
    deque <int> que;
    vector <int> dist(n + 1, infinity), prt(n + 1, -1), inq(n + 1, 0);

    dist[src] = 0, que.push_back(src), inq[src] = 1;
    for (; que.size(); que.pop_front()) {
        int x = que.front();
        for (int i = 0; i < (int)adj[x].size(); ++ i) {
            int y = adj[x][i];
            if (C[x][y] - F[x][y] > 0)
                if (dist[y] > dist[x] + Cst[x][y]) {
                    dist[y] = dist[x] + Cst[x][y];
                    prt[y]  = x;
                    if (!inq[y])
                        que.push_back(y), inq[y] = 1;
                }
        }
        inq[x] = 0;
    }
    if (prt[sink] != -1) {
        int f = infinity;
        for (int i = sink; i != src; i = prt[i])
            f = Min(f, C[prt[i]][i] - F[prt[i]][i]);
        for (int i = sink; i != src; i = prt[i])
            F[prt[i]][i] += f,
            F[i][prt[i]] -= f;
        return f * dist[sink];
    }
    return 0;
}

int main()
{
    read_in();
    int answer = 0, temp;
    while (true) {
        temp = BF();
        if (temp > 0)
            answer += temp;
        else
            break ;
    }
    ofstream out(oname);
    out << answer << "\n";
    out.close();

    return 0;
}