#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 cap[nmax][nmax];
int cost[nmax][nmax];
int dist[nmax];
int fdist[nmax];
int cdist[nmax];
int par[nmax];

void bellmanFord() {

  memset(fdist, inf, sizeof(fdist));
  
  static bool inq[nmax];
  queue<int> q;
  q.push(s);

  fdist[s] = 0;
  inq[s] = true;

  while (!q.empty()) {
    int u = q.front(); q.pop();
    inq[u] = false;
    for (int v : adj[u]) {
      if (cap[u][v] > 0 && fdist[u] + cost[u][v] < fdist[v]) {
        fdist[v] = fdist[u] + cost[u][v];
        if (!inq[v]) q.push(v), inq[v] = true;
      }
    }
  }
}

void dijkstra() {

  memset(dist, inf, sizeof(dist));
  memset(par, -1, sizeof(par));
  
  struct Edge {
    int node, dist;
    bool operator<(const Edge& p) const { return dist < p.dist; }
    bool operator>(const Edge& p) const { return dist > p.dist; }
  };

  priority_queue<Edge, vector<Edge>, greater<Edge>> pq;

  pq.push({s, 0});
  par[s] = 0;
  dist[s] = 0;
  cdist[s] = 0;

  while (!pq.empty()) {
    auto [u, d] = pq.top(); pq.pop();
    if (dist[u] < d) continue;
    for (int v : adj[u]) {
      if (cap[u][v] > 0) {
        int ndist = dist[u] + cost[u][v] + fdist[u] - fdist[v];
        if (ndist < dist[v]) {
          par[v] = u;
          dist[v] = ndist;
          cdist[v] = cdist[u] + cost[u][v];
          pq.push({v, dist[v]});
        }
      }
    }
  }

  memcpy(fdist, cdist, sizeof(fdist));
}

llong solve() {

  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);
    cap[u][v] = f;
    cost[u][v] = c;
    cost[v][u] = -c;
  }

  bellmanFord();

  if (fdist[d] > inf / 2) return 0;

  llong totalCost = 0;

  for (;;) {

    dijkstra();

    if (par[d] == -1) return totalCost;

    int currentFlow = INT_MAX;

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

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

    totalCost += (llong)currentFlow * fdist[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;
}