//AC
#include <iostream>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <math.h>
#include <string.h>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
typedef long long ll;
using namespace std;
int main(){
int n;
scanf("%d",&n);
printf("%.1f\n",(n-100)*0.9*2);
return 0;
}