#include <bits/stdc++.h>

using namespace std;

ifstream in("fmcm.in");
ofstream out("fmcm.out");

const int inf = (int)1e9 + 7;
const int max_n = (int)4e2 + 5;

int n, m;

int startNode, endNode;

bool visited[max_n];

int d[max_n];

int r[max_n][max_n];

int c[max_n][max_n];

vector<int> g[max_n];

int dad[max_n];

bool bfs(int startNode, int endNode) {
  for (int i = 1; i <= n; i++) {
    visited[i] = false;
    d[i] = inf;
    dad[i] = -1;
  }
  queue<int> q;
  q.push(startNode);
  visited[startNode] = true;
  d[startNode] = 0;
  while ((int)q.size() > 0) {
    int u = q.front();
    q.pop();
    visited[u] = false;
    for (int v : g[u]) {
      if (r[u][v] > 0 && d[v] > d[u] + c[u][v]) {
        d[v] = d[u] + c[u][v];
        dad[v] = u;
        if (!visited[v]) {
          visited[v] = true;
          q.push(v);
        }
      }
    }
  }
  return d[endNode] != inf;
}

int main() {
  in >> n >> m >> startNode >> endNode;
  for (int i = 1; i <= m; i++) {
    int u, v, cost, f;
    in >> u >> v >> f >> cost;
    r[u][v] = f;
    c[u][v] = cost;
    c[v][u] = -cost;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  int flow = 0;
  while (bfs(startNode, endNode) == true) {
    int f = inf;
    for (int u = endNode; u != startNode; u = dad[u]) {
      f = min(f, r[dad[u]][u]);
    }
    for (int u = endNode; u != startNode; u = dad[u]) {
      r[dad[u]][u] -= f;
      r[u][dad[u]] += f;
    }
    flow += f * d[endNode];
  }
  out << flow << "\n";
  return 0;
}