Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

void fnInput(int& rnMaxNum)
{
  cin >> rnMaxNum;
}

int64_t fnToInt(const vector<char>& cnrvcNum)
{
  const vector<int> cnvnDgt = {0, 3, 5, 7};
  int64_t nRtn = 0;
  int nNumPos = 0;

  for (int i = cnrvcNum.size() - 1; i >= 0; i--)
  {
    if (cnrvcNum[i] == '0') break;
    nRtn += cnvnDgt[ cnrvcNum[i] - '0' ] * pow(10.0, nNumPos++);
  }

  return nRtn;
}

int fnDgt753_Check(const vector<char>& cnrvcNum)
{
  int nDig3 = 0, nDig5 = 0, nDig7 = 0;

  for (int i = 0; i < cnrvcNum.size(); i++)
    if      (cnrvcNum[i] == '1') nDig3++;
    else if (cnrvcNum[i] == '2') nDig5++;
    else if (cnrvcNum[i] == '3') nDig7++;

  if (nDig3 && nDig5 && nDig7)
    return 1;
  else
    return 0;
}

int fnDgt753_Count(int nMaxNum)
{
  int nDgt753Cnt = 0;
  int nDgtSiz = to_string(nMaxNum).size();
  vector<char> vcNum(nDgtSiz + 1, '0');

  while (fnToInt(vcNum) <= nMaxNum) 
  {
    if (fnDgt753_Check(vcNum)) nDgt753Cnt++;

    vcNum[vcNum.size() - 1]++;
    for (int i = vcNum.size() - 1; i > 0; i--)
      if (vcNum[i] > '3')
      {  
        vcNum[i - 1]++;
        vcNum[i] = '1';
      }
      else
        break;
  }

  return nDgt753Cnt;
}

int main()
{
  int nMaxNum;

  fnInput(nMaxNum);
  cout << fnDgt753_Count(nMaxNum) << endl;

  return 0;
}