//#include <bits/stdc++.h>

#include <iostream>
#include <algorithm>

#include <bitset>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <cstring>
#include <string>
#include <utility>
#include <array>
#include <complex>
#include <valarray>

#include <cassert>
#include <cmath>
#include <functional>
#include <iomanip>
#include <chrono>
#include <random>
#include <numeric>


using namespace std;
#define int long long

typedef long long ll;
typedef unsigned long long ull;
//typedef unsigned __int128 HASH;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll,int> plli;
typedef pair<double, int> pdbi;
typedef pair<int,pii> pipii;
typedef pair<ll,pll> plpll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;
typedef vector<vector<int>> mat;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()

const ll hmod1 = 999999937;
const ll hmod2 = 1000000000 + 9;
const int INF = 1<<30;
const ll INFLL = 1LL<<62;
const double EPS = 1e-12;
const ll mod = 1000000000 + 7;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dy8[8] = {0, 1, -1, 1, -1, 0, 1, -1};
const double pi = 3.141592653589793;

#define addm(X, Y) (X) = ((X) + ((Y) % mod) + mod) % mod
#define inside(y, x, h, w) (0 <= (y) && (y) < (h) && 0 <= (x) && (x) < (w)) ? true : false

//debug
#define DEBUG

#define DUMPOUT cout

#ifdef DEBUG
#define dump(...) DUMPOUT<<#__VA_ARGS__<<" :["<<__FUNCTION__<<":"<<__LINE__<<"]"<<endl; DUMPOUT<<"    "; dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif

void dump_func() {DUMPOUT << endl;};

template <class Head, class... Tail> void dump_func(Head&& head, Tail&&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) == 0) DUMPOUT << " ";
    else DUMPOUT << ", ";
    dump_func(std::move(tail)...);
}

//ostream
template<typename T> ostream& operator << (ostream& os, vector<T>& vec) {
    os << "["; for (int i = 0; i<vec.size(); i++) os << vec[i] << (i + 1 == vec.size() ? "" : ", "); os << "]";
    return os;
}

template<typename T, typename U> ostream& operator << (ostream& os, pair<T, U>& pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

template<typename T, typename U> ostream& operator << (ostream& os, map<T, U>& map_var) {
    os << "[";
    for (auto itr = map_var.begin(); itr != map_var.end(); itr++) {
        os << "(" << itr->first << ", " << itr->second << ")"; itr++;  if(itr != map_var.end()) os << ", "; itr--;
    }
    os << "]";
    return os;
}

template<typename T> ostream& operator << (ostream& os, set<T>& set_var) {
    os << "[";
    for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {
        os << *itr; ++itr; if(itr != set_var.end()) os << ", "; itr--;
    }
    os << "]";
    return os;
}

int n, m, s, t;

struct edge1{int to, cost, id;};
vector<vector<edge1>> G(200 + 5), rG(205);
bool use_e[2005];

vector<ll> dijkstra(int s, int n, vector<vector<edge1>>& g){
    priority_queue<plli, vector<plli>, greater<plli>> pque;
    vector<ll> d(n, INFLL);
    d[s] = 0;
    pque.push(plli(0, s));

    while (!pque.empty()){
        plli p = pque.top(); pque.pop();
        int fr = p.second;
        if (d[fr] < p.first) continue;
        for (edge1 e: g[fr]){
            if (d[e.to] > d[fr] + e.cost){
                d[e.to] = d[fr] + e.cost;
                pque.push(plli(d[e.to], e.to));
            }
        }
    }
    return d;
}

const int MAX_V = 205;

struct edge {
    int to, cap, rev;
    edge(int to, int cap, int rev) :to(to), cap(cap), rev(rev) {}
};

vector<vector<edge>> g(MAX_V);
int level[MAX_V];
int iter[MAX_V];

void add_edge(int from, int to, int cap) {
    g[from].emplace_back(to, cap, g[to].size());
    g[to].emplace_back(from, 0, g[from].size() - 1);
}

void bfs(int s) {
    memset(level, -1, sizeof(level));
    queue<int> q;
    level[s] = 0;
    q.push(s);
    while (!q.empty()) {
        int now = q.front(); q.pop();
        for (auto e : g[now]) {
            if (e.cap > 0 && level[e.to] < 0) {
                level[e.to] = level[now] + 1;
                q.push(e.to);
            }
        }
    }
}

int dfs(int now, int t, int f) {
    if (now == t) return f;
    for (int &i = iter[now]; i < g[now].size(); i++) {
        edge &e = g[now][i];
        if (e.cap > 0 && level[now] < level[e.to]) {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0) {
                e.cap -= d;
                g[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}

int max_flow(int s, int t) {
    int flow = 0;
    while (true) {
        bfs(s);
        if (level[t] < 0) return flow;
        memset(iter, 0, sizeof(iter));
        int f;
        while ((f = dfs(s, t, INF)) > 0) flow += f;
    }
}
int u[2005], v[2005], d[2005], c[2005];

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n >> m >> s >> t;
    s--; t--;
    rep(i, m) {
        cin >> u[i] >> v[i] >> d[i] >> c[i];
        u[i]--; v[i]--;
        G[u[i]].push_back({v[i], d[i], i});
        rG[v[i]].push_back({u[i], d[i], i});
    }
    vector<ll> dist = dijkstra(s, n, G);
    queue<int> q;
    q.push(t);
    bool visited[205] = {};
    //bool visited_e[2005] = {};
    visited[t] = true;
    while (!q.empty()) {
      int now = q.front(); q.pop();
      for (edge1 nx : rG[now]) {
        if (dist[now] - dist[nx.to] == nx.cost) {
          use_e[nx.id] = true;
          if (visited[nx.to]) continue;
          visited[nx.to] = true;
          q.push(nx.to);
        }
      }
    }
    rep(i, m) {
      if (!use_e[i]) continue;
      add_edge(u[i], v[i], c[i]);
    }
    cout << max_flow(s, t) << endl;
}



Measured memory_bytes: 3416