AtCoder ABC 755

atcoder_abc755.cc

#include <iostream>
using namespace std;

int generate_and_count(long long current, long long target, bool has3, bool has5, bool has7) {
  int answer = 0;
  if (current > target) {
    return answer;
  }
  if (has3 && has5 && has7) {
    answer++;
  }
  answer += generate_and_count(current * 10 + 3, target, true, has5, has7);
  answer += generate_and_count(current * 10 + 5, target, has3, true, has7);
  answer += generate_and_count(current * 10 + 7, target, has3, has5, true);
  return answer;
}

int main() {
  int N;
  cin >> N;

  cout << generate_and_count(0, N, false, false, false) << endl;
}