#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	if(n<=150) printf("%.1f",n*0.4463);
	else if(n>=151&&n<=400) printf("%.1f",(150*0.4463)+(n-150)*0.4663);
	else printf("%.1f",(150*0.4463)+(400-150)*0.4663+(n-400)*0.5663);
}
/**************************************************************
	Problem: 1463
	User: linzihang
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/