#include<bits/stdc++.h>
using namespace std;
int main(){
	double n;
	cin>>n;
	if(n<=151){
		printf("%.1lf",n*0.4463);
	}else if(n<=401){
		printf("%.1lf",(150*0.4463)+((n-150)*0.4663));
	}else{
		printf("%.1lf",(150*0.4463)+(400*0.4663)+((n-400)*0.5663));
	}
}