백준 1065 - 한수

#include <iostream>
 
using namespace std;
 
bool isHan(int n) {
    int a, b, c;
    
    if(n < 100)
        return true;
    a = n/100;
    b = (n%100)/10;
    c = n%10;
    
    if(a-b == b-c)
        return true;
    else
        return false;
}
 
int main(void) {
    int N, result=0;
    cin >> N;
    
    for(int i=1; i<=N; i++) {
        if(isHan(i))
            result++;
    }
    cout << result;
    
    return 0;
}