#include <bits/stdc++.h>
using namespace std;
int main(){
	int kw;
	float money;
	scanf("%d",&kw);
	if (kw<=150) {
		money=kw*0.4463;
	}else if(kw<=400){
		money=150*0.4463+(kw-150)*0.4663;
	}else{
		money=150*0.4463+250*0.4663+(kw-400)*0.5663;
	}
	printf("%.1f",money);
	return 0;
}

/**************************************************************
	Problem: 1463
	User: lzk
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2076 kb
****************************************************************/