#include <cstdio>
#include <vector>
#include <queue>
#include <algorithm>
#include <iostream>

using namespace std;

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

void add(int a, int b, int cp, int cst) {
  g[a].push_back(b);
  g[b].push_back(a);
  cap[a][b] = cp;
  cost[a][b] = cst;
  cost[b][a] = -cst;
}

bool cmp() { /// do it later

}

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

  scanf("%d %d %d %d", &n, &m, &s, &d);
  for (int i = 1; i <= m; i++) {
    int a, b, c, d;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    add(a, b, c, d);
  }
  ll sol = 0;
  while (1) {
    for (int i = 1; i <= n; i++) {
      dmin[i] = INF;
      par[i] = -1;
    }
    dmin[s] = 0;
    mn[s] = INF;
    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] > 0 && dmin[a] + cost[a][b] < dmin[b]) {
          dmin[b] = dmin[a] + cost[a][b];
          par[b] = a;
          mn[b] = min(cap[a][b], mn[a]);
          if (!inq[b]) {
            q.push(b);
            inq[b] = 1;
          }
        }
      }
    }
    if (par[d] == -1) {
      break;
    }
    sol += (ll) mn[d] * dmin[d];
    int val = mn[n];
    int node = d;
    vector<int> path;
    while (1) {
      path.push_back(node);
      if (node == s) {
        break;
      }
      node = par[node];
    }
    reverse(path.begin(), path.end());
    for (int i = 0; i + 1 < (int) path.size(); i++) {
      cap[path[i]][path[i + 1]] -= mn[d];
      cap[path[i + 1]][path[i]] += mn[d];
    }
  }
  printf("%lld\n", sol);
}