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

const int nmax = 357;
const int inf = 0x3f3f3f3f;

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

void bellmanFord() {

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

void dijkstra() {

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

  priority_queue<Pos> pq;
  pq.push({s, 0});
  dist[s] = 0;
  cdist[s] = 0;

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

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

}

void 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();

  typedef long long llong;

  llong totalCost = 0;

  for (;;) {
  
    dijkstra();

    if (par[d] == -1) break;

    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];

  }

  cout << totalCost << endl;

}

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);

  solve();
}