#include <bits/stdc++.h>
using namespace std;
const int MAXF = 20;
long long f[MAXF];
int a[MAXF];
int p[MAXF];
bool isLucky(long long x) {
  do
    if (x % 10 != 4 && x % 10 != 7) return false;
  while (x /= 10);
  return true;
}
long long count(long long n) {
  long long res = 0;
  ;
  for (int i = 1; i <= 10; i++) {
    for (int j = 0; j < (1 << i); j++) {
      long long x = 0;
      for (int k = i - 1; k >= 0; k--) {
        (x *= 10) += 4;
        if (j & (1 << k)) x += 3;
      }
      if (x > n) return res;
      res++;
    }
  }
  return res;
}
int main() {
  long long n, m, k;
  scanf("%I64d %I64d", &n, &k);
  f[0] = 1;
  for (int i = 1; i < MAXF; i++) f[i] = f[i - 1] * i;
  for (m = 0; k > f[m]; m++)
    ;
  if (m > n) {
    puts("-1");
    return 0;
  }
  n -= m;
  long long ans = count(n);
  k--;
  for (int i = 0; i < m; i++) a[i] = i;
  for (int i = 0; i < m; i++) {
    int t = k / f[m - i - 1];
    k %= f[m - i - 1];
    p[i] = a[t];
    for (int j = t; j < m - i; j++) a[j] = a[j + 1];
  }
  for (int i = 0; i < m; i++) {
    if (isLucky(n + i + 1) && isLucky(n + p[i] + 1)) ans++;
  }
  printf("%I64d\n", ans);
  fprintf(stderr, "Time of execution: %.3lf sec.\n",
          (double)clock() / CLOCKS_PER_SEC);
  return 0;
}
