#include <iostream>
#include <iomanip>
using namespace std;
int main() {
    int n;
    cin >> n;
    double p;
    if (n >= 10) {
        p = n * 2.0;
    } else {
        p = n * 2.2;
    }
	printf("%.1f",p);
    return 0;
}
/**************************************************************
	Problem: 1303
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/