#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	float s;
	if(n>=10){
		s=2.0*n;
	}
	else{
		s=2.2*n;
	}
	printf("%.1f",s);
	
	
	
}
/**************************************************************
	Problem: 1303
	User: fandaohan
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/