#include <bits/stdc++.h>
using namespace std;
const long double PI = 3.14159265358979323;
const long long int linf = 1000111000111000111LL;
const long long int inf = 1011111111;
const long long int N = 100005;
vector<long long int> v1[10], v2;
set<long long int> st2;
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int test = 1;
  while (test--) {
    long long int n, k;
    cin >> n >> k;
    long long int fac[13];
    fac[0] = 1;
    for (long long int i = 1; i <= 12; i++) fac[i] = fac[i - 1] * i;
    if (n <= 12) {
      if (k > fac[n]) {
        cout << "-1\n";
        continue;
      }
    }
    v1[1].push_back(4);
    v1[1].push_back(7);
    for (long long int i = 2; i <= 9; i++) {
      for (long long int j = 0; j < (long long int)(v1[i - 1]).size(); j++) {
        v1[i].push_back(v1[i - 1][j] * 10 + 4);
        v1[i].push_back(v1[i - 1][j] * 10 + 7);
      }
    }
    for (long long int i = 1; i <= 9; i++) {
      for (long long int j = 0; j < (long long int)(v1[i]).size(); j++) {
        v2.push_back({v1[i][j]});
        st2.insert(v1[i][j]);
      }
    }
    long long int ans = 0;
    if (n > 13) {
      long long int ele = n - 13;
      long long int p1 =
          upper_bound((v2).begin(), (v2).end(), ele) - v2.begin();
      ans += p1;
    }
    set<long long int> st1;
    for (long long int i = n; i >= max((long long int)1, n - 12); i--)
      st1.insert(i);
    long long int pos = max((long long int)1, n - 12);
    while (!st1.empty()) {
      long long int len = (long long int)(st1).size();
      long long int q1 = fac[len - 1];
      long long int num = k / q1;
      if (k % q1 != 0) num++;
      auto it = st1.begin();
      for (long long int i = 0; i < num - 1; i++) it++;
      long long int ele = *it;
      st1.erase(ele);
      if (st2.find(ele) != st2.end() and st2.find(pos) != st2.end()) ans++;
      pos++;
      k = k % q1;
      if (k == 0) k = q1;
    }
    cout << ans << "\n";
  }
  cerr << '\n'
       << "Time elapsed :" << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}
