#include <bits/stdc++.h>
using namespace std;
const int INF = 1000 * 1000 * 1000;
const long long INF64 = 1000LL * 1000LL * 1000LL * 1000LL * 1000LL * 1000LL;
int n;
long long k;
inline bool is_lucky(int x) {
  while (x > 0) {
    if (x % 10 == 4 || x % 10 == 7)
      x /= 10;
    else
      return false;
  }
  return true;
}
void Load() { cin >> n >> k; }
int mark[20];
int a[20];
int pos[20];
long long fac[20];
vector<long long> g;
string s = ".....................";
void rec(int pos) {
  if (pos > 10) return;
  long long x = 0;
  for (int i = 0; i < pos; i++) x = x * 10 + s[i] - '0';
  g.push_back(x);
  s[pos] = '4';
  rec(pos + 1);
  s[pos] = '7';
  rec(pos + 1);
}
void Solve() {
  fac[0] = 1;
  for (int i = 1; i < 15; i++) {
    fac[i] = fac[i - 1] * i;
  }
  if (n < 14 && fac[n] < k) {
    cout << -1;
    return;
  }
  rec(0);
  sort(g.begin(), g.end());
  int ans = 0;
  int m = max(n - 13, 1);
  int sz = 0;
  for (int i = 1; i < (int)g.size(); i++) {
    if (g[i] >= m) break;
    ans++;
  }
  for (int i = m; i <= n; i++) {
    a[i - m] = i;
    sz++;
  }
  for (int i = 1; i <= sz; i++) {
    for (int j = 0; j < sz; j++)
      if (!mark[j]) {
        if (fac[sz - i] < k)
          k -= fac[sz - i];
        else {
          mark[j] = 1;
          if (is_lucky(a[j]) && is_lucky(m + i - 1)) ans++;
          break;
        }
      }
  }
  cout << ans;
}
int main() {
  Load();
  Solve();
  return 0;
}
