#include<iostream>

using namespace std;

int main()
{int i=100,sam=0;
while(i>=1){
	sam+=i;
	
	
	i-=3;
}
cout<<sam<<endl;
	return 0;
}
/**************************************************************
	Problem: 1053
	User: ct001
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/