#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a;
	float rasult;
	cin>> a;
	if(a>=10){
	rasult=a*2;
	}else{
		rasult=a*2;
	}
      printf("%.1f",rasult);
	return 0;
}
/**************************************************************
	Problem: 1303
	User: ct001
	Language: C++
	Result: Wrong Answer
****************************************************************/