#include <bits/stdc++.h>

using namespace std;

using T = int;
const T INF = numeric_limits<T>::max() / 4;

struct MFMC {
  struct Edge { int from, to; T flow, cap, cost; };
  
  int n;
  vector<T> dist, pi;
  vector<int> par; vector<vector<int>> graph;
  vector<Edge> es;
  
  MFMC(int n) : n(n), pi(n, 0), par(n, -1), graph(n) {}
  
  void AddEdge(int a, int b, T cap, T cost) {
    auto add = [&](int a, int b, T cap, T cost) {
      es.push_back({a, b, 0, cap, cost});
      graph[a].push_back(es.size() - 1);
    };
    add(a, b, cap, cost); add(b, a, 0, -cost);
  }
  bool relax(int ei) {
    const auto &e = es[ei];
    if (dist[e.from] == INF) return false;
    T now = dist[e.from] + pi[e.from] - pi[e.to] + e.cost;
    if (e.flow < e.cap && now < dist[e.to]) {
      dist[e.to] = now; par[e.to] = ei;
      return true;
    }
    return false;
  }
  bool dijkstra(int s, int t) {
    dist.assign(n, INF); par.assign(n, -1);
    priority_queue<pair<T, int>> pq; 
    dist[s] = 0; pq.emplace(0, s); 
    while (!pq.empty()) {
      T d; int node; tie(d, node) = pq.top(); pq.pop(); 
      // auto [d, node] = pq.top(); pq.pop();
      if (dist[node] != -d) continue;
      for (auto ei : graph[node]) 
        if (relax(ei)) 
          pq.emplace(-dist[es[ei].to], es[ei].to);
    }
    for (int i = 0; i < n; ++i) {
      assert(dist[i] >= 0);
      pi[i] = min(pi[i] + dist[i], INF);
    }
    return par[t] != -1;
  }
  pair<T, T> Compute(int s, int t) {
    T flow = 0, cost = 0;
    while (dijkstra(s, t)) {
      T now = INF;
      for (int ei = par[t]; ei != -1; ei = par[es[ei].from]) 
        now = min(now, es[ei].cap - es[ei].flow);
      assert(now > 0);
      for (int ei = par[t]; ei != -1; ei = par[es[ei].from]) {
        es[ ei ].flow += now;
        es[ei^1].flow -= now;
        cost += es[ei].cost * now;
      }
      flow += now;
    }
    return {flow, cost};
  }
  // If some costs can be negative, call this before maxflow:
  void SetPi(int s) { // (otherwise, leave this out)
    dist.assign(n, INF); dist[s] = 0;
    int it = n, ch = 1;
    while (ch-- && it--)
      for (int ei = 0; ei < (int)es.size(); ++ei) 
        ch |= relax(ei);
    assert(it >= 0); // negative cost cycle
    swap(pi, dist);
  }
  void SetPi2(int s) {
    pi.assign(n, INF);
    vector<int> q;
    vector<bool> inq(n, false);
    auto push = [&](int node, T d) {
      if (pi[node] <= d) return;
      pi[node] = d;
      if (!inq[node]) inq[node] = true, q.push_back(node);
    };
    push(s, 0);
    for (int i = 0; i < (int)q.size(); ++i) {
      for (auto ei : graph[q[i]]) {
        const auto& e = es[ei];
        if (e.cap) push(e.to, pi[q[i]] + e.cost);
      }
    }
  }
};

int main() {
  ifstream cin("fmcm.in");
  ofstream cout("fmcm.out");

  int n, m, s, t; cin >> n >> m >> s >> t;
  MFMC F(n);
  for (int i = 0; i < m; ++i) {
    int a, b, c, k; cin >> a >> b >> c >> k;
    F.AddEdge(a - 1, b - 1, c, k);
  }
  F.SetPi2(s - 1);
  cout << F.Compute(s - 1, t - 1).second << endl;
  return 0;
}