#define _CRT_SECURE_NO_WARNINGS
//#pragma comment(linker, "/STACK:100000000")
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cmath>
#include <string>
#include <cstring>
#include <set>
#include <stdio.h>
#include <vector>
#include <map>
#include <time.h>

#define ll long long
#define ld long double
#define f(i, a, b) for(int i=(int)(a); i<(int)(b); ++i)
#define fn(i, b) for(int i=0; i<(int) (b); i++)
#define fz(i, a, b) for (int i=(int)(a); i>=(int)(b); --i)
#define mp make_pair
#define pii pair<int, int>
#define pb push_back
#define bg begin()
#define ed end()
#define pi 3.141592653589793238462643383279
int gcd(int a, int b) {
  if (b == 0)
      return a;
  else
      return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return ((a / gcd(a, b))*b); }


#define MAX 1010 //53
#define INF 1e5
#define y1 yy1
#define eps 0.01
void out(std::string s){ std::cout << s << "\n"; exit(0); }
ll sqr(ll A) { return A*A; };
#define ls (v << 1)
#define rs (v << 1)+1
using namespace std;

int n, k, a, b, d, x, y;
vector<int> g[MAX];
bool used[MAX];
int ans = 0;

void dfs(int v, int height){
  if (height > d) return;
if (used[v]) return;
used[v]=1;
  if (v == b) {
      ans++;
      return;
  }
  fn(i, g[v].size()) dfs(g[v][i], height + 1);

}

int main(){
  freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);

  cin >> n >> k >> a >> b >> d;
  fn(i, k) {
      cin >> x >> y;
      g[x].pb(y);
      //g[y].pb(x);
  }
  ans = 0;
  dfs(a, 0);
  cout << ans << endl;

  return 0;
}