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

int main() {
int N;
cin >> N;
if (N <= 9){;
cout << 18;
return 0;
}
if (N <= 99){;
cout << 27;
return 0;
}
if (N <= 999){;
cout << 36;
return 0;
}
if (N <= 9999){;
cout << 45;
return 0;
}
if (N <= 99999){;
cout << 54;
return 0;
}
if (N <= 999999){;
cout << 63;
return 0;
}
if (N <= 9999999){;
cout << 72;
return 0;
}
if (N <= 99999999){;
cout << 81;
return 0;
}
if (N <= 999999999){;
cout << 90;
}
return 0;
}