#include <iostream>
using namespace std;
int main()
{
	int n;
	cin >> n;
	if (n>=90)
	{
		cout << 3*n;	
	}
	else if (80<=n && n<90)
	{
		cout << 2*n;
	}
	else if (70<=n && n<80)
	{
		cout << n;
	}
	else
	{
		cout << 50;
	}
}
/**************************************************************
	Problem: 1300
	User: xiaomingze
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/