111111

#include <stdio.h>
int main(){

    double a ,s;
    scanf("%lf",&a);
    if(a - (int)a!=0){
    	a = (int)a+1;
    }
    if(a>20){
    	s = 20*1.68+(a-20)*1.98;
    }else{
    	s = a*1.68;
    }
    printf("%.2lf",s);
	return 0 ;
}