#include <iostream>
using namespace std;
int main(void){
    int n;
    cin>>n;
    if (n<10) {
        cout<<n<<"\n";
    } else if (n<30) {
        cout<<((n-10)%2?(n-10+1)/2-1:1)<<"\n";
    } else if (n<50) {
        cout<<((n-30)%2?(n-30+1)/2-1:2)<<"\n";
    } else if (n<70) {
        cout<<((n-50)%2?(n-50+1)/2-1:3)<<"\n";
    } else if (n<90) {
        cout<<((n-70)%2?(n-70+1)/2-1:4)<<"\n";
    } else {
        cout<<((n-90)%2?(n-90+1)/2-1:5)<<"\n";
    }
    return 0;
}