#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 350 + 7;
const int INF = (int) 1e9;
int n, m, s, d, cap[N][N], cost[N][N], minDist[N], minCap[N], par[N];
vector<int> g[N];
bool inq[N];

int main() {
  //freopen ("input", "r", stdin);
  freopen ("fmcm.in", "r", stdin), freopen ("fmcm.out", "w", stdout);

  cin >> n >> m >> s >> d;
  for (int i = 1; i <= m; i++) {
    int x, y;
    cin >> x >> y;
    cin >> cap[x][y] >> cost[x][y];
    cost[y][x] = -cost[x][y];
    g[x].push_back(y);
    g[y].push_back(x);
  }

  int maxflow = 0;
  ll mincost = 0;

  while (1) {
    for (int i = 1; i <= n; i++) {
      minDist[i] = INF;
    }
    minCap[s] = INF;
    minDist[s] = 0;
    queue<int> q;
    q.push(s);
    inq[s] = 1;
    while (!q.empty()) {
      int a = q.front();
      inq[a] = 0;
      q.pop();
      for (auto &b : g[a]) {
        if (!cap[a][b]) continue;
        int upd = minDist[a] + cost[a][b];
        if (upd < minDist[b]) {
          minDist[b] = upd;
          minCap[b] = min(minCap[a], cap[a][b]);
          par[b] = a;
          if (!inq[b]) {
            q.push(b);
            inq[b] = 1;
          }
        }
      }
    }
    if (minDist[d] == INF) {
      break;
    }
    maxflow += minCap[d];
    mincost += (ll) minDist[d] * minCap[d];
    vector<int> path;
    {
      int vertex = d;
      while (vertex != s) {
        path.push_back(vertex);
        vertex = par[vertex];
      }
      path.push_back(s);
      reverse(path.begin(), path.end());
    }
    for (int i = 0; i + 1 < (int) path.size(); i++) {
      int x = path[i], y = path[i + 1];
      cap[x][y] -= minCap[d];
      cap[y][x] += minCap[d];
    }
  }

 // cout << maxflow << "\n";
  cout << mincost << "\n";


  return 0;
}