#include <bits/stdc++.h>
using namespace std;
double PI = 3.141592653589793;
const int mx = 13;
long long cnt[mx + 1];
int val[mx + 1];
bool lck(int n) {
  bool out = 1;
  while (n != 0) {
    if (n % 10 != 4 && n % 10 != 7) out = 0;
    n /= 10;
  }
  return out;
}
const int bmx = 9;
vector<int> proc;
void init() {
  for (int i = 1; i < bmx + 1; i++) {
    for (int j = 0; j < (1 << i); j++) {
      int val = 0;
      for (int k = 0; k < i; k++) {
        if (j & (1 << k))
          val = 10 * val + 7;
        else
          val = 10 * val + 4;
      }
      proc.push_back(val);
    }
  }
}
void solve() {
  init();
  int n, k;
  cin >> n >> k;
  k--;
  cnt[0] = 1;
  for (int i = 1; i < mx + 1; i++) cnt[i] = cnt[i - 1] * i;
  if (n <= mx && k + 1 > cnt[n]) {
    cout << -1;
    return;
  }
  set<int> done;
  for (int i = 0; i < mx + 1; i++) {
    long long ccnt = 0, ind = 0;
    while (done.count(ind)) ind++;
    while (ccnt + cnt[mx - i] <= k) {
      ccnt += cnt[mx - i];
      ind++;
      while (done.count(ind)) ind++;
    }
    k -= ccnt;
    val[i] = ind;
    done.insert(ind);
  }
  int ans = 0;
  if (n <= mx + 1) {
    for (int i = mx - n + 1; i <= mx; i++) {
      int in = i - (mx - n);
      int v = val[i] - (mx - n);
      if (lck(in) && lck(v)) ans++;
    }
  } else {
    int st = n - mx;
    for (auto i : proc) ans += (i < st);
    for (int i = 0; i <= mx; i++) {
      int in = st + i;
      int v = st + (val[i]);
      if (lck(in) && lck(v)) ans++;
    }
  }
  cout << ans;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int T = 1;
  for (int c = 1; c < T + 1; c++) {
    solve();
  }
}
