#include <bits/stdc++.h>
using namespace std;

const int nmax = 357;
const int inf = 0x3f3f3f3f;
typedef long long llong;

int n, m, s, d;
vector<int> adj[nmax];
int flow[nmax][nmax];
int cost[nmax][nmax];
int dist[nmax];
int par[nmax];

void bellmanFord() {

  memset(dist, inf, sizeof(dist));
  memset(par, -1, sizeof(par));

  dist[s] = 0;

  for (int rep = 0; rep < n; rep++) {
    for (int u = 1; u <= n; u++) {
      for (int v : adj[u]) {
        if (flow[u][v] > 0 && dist[u] + cost[u][v] < dist[v]) {
          par[v] = u;
          dist[v] = dist[u] + cost[u][v];
        }
      }
    }
  }

}

llong solve() {

  memset(cost, inf, sizeof(cost));

  cin >> n >> m >> s >> d;

  for (int i = 0; i < m; i++) {
    int u, v, f, c;
    cin >> u >> v >> f >> c;
    adj[u].push_back(v);
    adj[v].push_back(u);
    flow[u][v] = f;
    cost[u][v] = c;
    cost[v][u] = -c;
  }

  llong totalCost = 0;

  for (;;) {

    bellmanFord();

    if (dist[d] > inf / 2) return totalCost;

    int currentFlow = INT_MAX;

    for (int u = d; u != s; u = par[u]) {
      currentFlow = min(currentFlow, flow[par[u]][u]);
    }

    for (int u = d; u != s; u = par[u]) {
      flow[par[u]][u] -= currentFlow;
      flow[u][par[u]] += currentFlow;
    }

    totalCost += llong(currentFlow) * llong(dist[d]);

  }

}

int main() {
  
  #ifdef LOCAL
  freopen("file.in", "r", stdin);
  #else
  freopen("fmcm.in", "r", stdin);
  freopen("fmcm.out", "w", stdout);
  #endif

  ios_base::sync_with_stdio(false), cin.tie(NULL);

  cout << solve() << endl;
}