#include <stdio.h>
void main()
{
	int n;
	double p;
	scanf("%d",&n);
	if(n>=10)
	{
		p=n*2;
	}else{
		p=n*2.2;
	}
	printf("%.1f",p);
}
/**************************************************************
	Problem: 1303
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1144 kb
****************************************************************/