#include <stdio.h>

 

void main(){

    int n;

    scanf("%d",&n);

    printf("%.1f%%",(2*n-1+4) * 100.0 / (n * n));

}
/**************************************************************
	Problem: 1345
	User: admin
	Language: C
	Result: Accepted
	Time:8 ms
	Memory:1144 kb
****************************************************************/