#include<bits/stdc++.h>
using namespace std;
const int L=100000;
int main(){
	int qws;
	cin>>qws;
	double n=0.0;
	for(int i=0;i<qws;i++){
		if(i<=150){
			n+=0.4463;
		}if(i>=151 && i<=400){
			n+=0.4663;
		}if(i>=401){
			n+=0.5663;
		}
	}printf("%.1lf", n);
}