#include<bits/stdc++.h>
using namespace std;
int main()
{
	double d,m;
	cin>>d;
		if(d<=150)
		{
			m=d*0.4463;
			printf("%.1lf",m);
		}
		else
			if(d<=400)
			{
				m=(d-150)*0.4663+150*0.4463;
				printf("%.1lf",m);
			}
		else
			if(d>400)
			{
				m=(d-400)*0.5663+249*0.4663+150*0.4463;
				printf("%.1lf",m);
			}
	return 0;
}