#include<stdio.h>
int main(){
int n,a,b,c,d,e,g;
scanf("%d",&n);
a = n / 2;
b = ((n % 2)+ (a / 2));
e = b / 2;
c = (b / 2);
d = c;
g = n + a + e + d;
printf("%d",g);
return 0;
}