#include <bits/stdc++.h>
using namespace std;
const int MAX = 1000000000;
set<long long> st;
vector<long long> vec;
int N, K;
long long fac[20];
int num[20];
bool use[20];
void Init(long long x) {
  if (x < MAX) {
    st.insert(x * 10 + 4);
    Init(x * 10 + 4);
    st.insert(x * 10 + 7);
    Init(x * 10 + 7);
  }
}
void make_dp(int K, int m) {
  memset(use, 0, sizeof(use));
  for (int i = 1; i <= m; ++i) {
    int cnt = m - i;
    for (int j = m;; --j) {
      if (!use[j]) {
        if (cnt * fac[m - i] >= K) {
          --cnt;
        } else {
          use[j] = 1;
          num[i] = j;
          K -= cnt * fac[m - i];
          break;
        }
      }
    }
  }
}
bool luck_number(int x) {
  if (x <= 0) {
    return 0;
  }
  while (x) {
    if (x % 10 != 4 && x % 10 != 7) {
      return 0;
    }
    x /= 10;
  }
  return 1;
}
int main() {
  Init(0);
  for (set<long long>::iterator it = st.begin(); it != st.end(); ++it) {
    vec.push_back(*it);
  }
  fac[1] = 1;
  for (int i = 2; i < 20; ++i) {
    fac[i] = fac[i - 1] * i;
  }
  while (cin >> N >> K) {
    if (N < 19 && fac[N] < K) {
      puts("-1");
      continue;
    }
    int m = 0;
    while (fac[m] < K) {
      m++;
    }
    N -= m;
    int ans = 0;
    for (int i = 0; vec[i] <= N; ++i) {
      ans++;
    }
    make_dp(K, m);
    for (int i = 1; i <= m; ++i) {
      if (luck_number(N + i) && luck_number(N + num[i])) {
        ans++;
      }
    }
    cout << ans << endl;
  }
  return 0;
}
