#include<stdio.h>

void main(){
	int x;
	double p;
	scanf("%d",&x);
	
	p=0.9*x;
	
	printf("%.1f",p);
}
/**************************************************************
	Problem: 1613
	User: admin
	Language: C
	Result: Accepted
	Time:8 ms
	Memory:1144 kb
****************************************************************/