#include <stdio.h>
#include <vector>
#include <queue>

#define maxdim 353

using namespace std;

int n, m, source, dest;
int cp[maxdim][maxdim], f[maxdim][maxdim], dist[maxdim], inq[maxdim], T[maxdim];
vector<pair<int, int>> G[maxdim];

int bf() {
  for (int i = 1; i <= n; ++i) {
    T[i] = 0;
    dist[i] = (1 << 29);
    inq[i] = 0;
  }

  queue<int> q;
  dist[source] = 0;
  q.push(source);
  inq[source] = 1;
  while (!q.empty()) {
    int nod = q.front(); q.pop();
    inq[nod] = 0;

    for (auto &p : G[nod]) {
      int vecin = p.first, cost = p.second;
      if (cp[nod][vecin] > f[nod][vecin] && dist[vecin] > dist[nod] + cost) {
        dist[vecin] = dist[nod] + cost;
        T[vecin] = nod;
        if (!inq[vecin]) {
          q.push(vecin);
          inq[vecin] = 1;
        }
      }
    }
  }
  return dist[dest] != (1 << 29);
}


int fmcm() {
  int flow_cost = 0;
  while (bf()) {
    int nod = dest;
    int crt_flow = (1 << 29);
    while (T[nod]) {
      crt_flow = min(crt_flow, cp[T[nod]][nod] - f[T[nod]][nod]);
      nod = T[nod];
    }
    nod = dest;
    while (T[nod]) {
      f[T[nod]][nod] += crt_flow;
      f[nod][T[nod]] -= crt_flow;
      nod = T[nod];
    }
    flow_cost += crt_flow * dist[dest];
  }
  return flow_cost;
}

int main() {
  freopen("fmcm.in", "r", stdin);
  freopen("fmcm.out", "w", stdout);
  
  scanf("%d %d %d %d", &n, &m, &source, &dest);
  for (int i = 1; i <= m; ++i) {
    int x, y, cap, cost; scanf("%d %d %d %d", &x, &y, &cap, &cost);
    cp[x][y] = cap;
    G[x].push_back(make_pair(y, cost));
    G[y].push_back(make_pair(x, -cost));
  }

  printf("%d\n", fmcm());

  return 0;
}