#include <bits/stdc++.h>
using namespace std;
vector<long long> v, ext;
long long f[20];
bool vis[20];
bool chck(long long j) {
  while (j) {
    if (j % 10 != 4 && j % 10 != 7) break;
    j /= 10;
  }
  return j == 0;
}
int main() {
  long long i, n, k, st, sum, j, pre, sz, ans;
  f[0] = 1;
  for (i = 1; i <= 13; i++) f[i] = f[i - 1] * i;
  cin >> n >> k;
  if (n <= 13 && k > f[n]) {
    cout << -1 << endl;
    return 0;
  }
  for (i = 1; f[i] < k; i++)
    ;
  st = n - i + 1;
  sum = k;
  for (j = 1; j <= i; j++) {
    for (k = st; k <= n; k++) {
      if (!vis[k - st]) {
        if (sum - f[i - j] > 0) {
          sum -= f[i - j];
        } else {
          ext.push_back(k);
          vis[k - st] = 1;
          break;
        }
      }
    }
  }
  queue<long long> q;
  q.push(4);
  q.push(7);
  v.push_back(4);
  v.push_back(7);
  while (!q.empty()) {
    pre = q.front();
    q.pop();
    if (pre * 10 + 4 <= 5000000000LL) {
      q.push(pre * 10 + 4);
      q.push(pre * 10 + 7);
      v.push_back(pre * 10 + 4);
      v.push_back(pre * 10 + 7);
    }
  }
  sz = v.size();
  ans = 0;
  for (i = 0; i < sz && v[i] < st; i++) ans++;
  for (i = st; i <= n; i++) {
    if (chck(i)) {
      if (chck(ext[i - st])) ans++;
    }
  }
  cout << ans << endl;
  return 0;
}
