#include <bits/stdc++.h>
using namespace std;
template <class T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const double EPS = 1e-9;
const double PI = acos(-1.);
const long long LL_INF = 1e17 + 16;
const int INF = 1e9 + 10;
const long long MOD = 1e9 + 7;
const int MAXN = 20;
set<long long> goods;
long long f[MAXN];
void gen() {
  for (int i = (1); i <= (int)(10); i++) {
    for (int j = (0); j < (int)(1 << i); j++) {
      long long v = 0;
      long long st10 = 1;
      for (int k = (0); k < (int)(i); k++) {
        if (j & (1 << k)) {
          v += 7 * st10;
        } else {
          v += 4 * st10;
        }
        st10 *= 10;
      }
      goods.insert(v);
    }
  }
}
int per[MAXN];
int used[MAXN];
void solve() {
  gen();
  long long n, k;
  cin >> n >> k;
  f[0] = 1;
  int m;
  for (m = 1;; m++) {
    f[m] = f[m - 1] * m;
    if (f[m] >= k) {
      break;
    }
  }
  if (m > n) {
    printf("-1\n");
    return;
  }
  int ans = 0;
  int offset = n - m;
  for (__typeof((goods).begin()) it = (goods).begin(); it != (goods).end();
       it++) {
    if ((*it) <= offset) {
      ans++;
    }
  }
  k--;
  int top = 1;
  for (int i = m; i >= 1; i--) {
    int v = k / f[i - 1] + 1;
    int cnt = 0;
    for (int j = (1); j <= (int)(m); j++) {
      if (!used[j]) {
        cnt++;
        if (cnt == v) {
          per[top++] = j;
          used[j] = 1;
          break;
        }
      }
    }
    k %= f[i - 1];
  }
  for (int i = (1); i <= (int)(m); i++) {
    if (goods.count(i + offset) && goods.count(per[i] + offset)) {
      ans++;
    }
  }
  cout << ans << endl;
}
int main() {
  int t = 1;
  while (t--) {
    solve();
  }
}
