题解 | #自守数#

#include <iostream>
using namespace std;

bool IsZiShouShu(int num)
{
    int m = num*num;
 
    while (num != 0){
        if (m % 10 != num % 10){
            return false;
        }
        else{
          
            m   = m / 10;
            num = num / 10;
        }
    }
    
    return true;
}

int main() {
    int n, cnt = 0;
    cin >> n;

    for (int i = 0; i <= n; i++){
        if (IsZiShouShu(i)){
            cnt++;
        }
    }
    cout << cnt <<endl;
}