#include<bits/stdc++.h>
using namespace std;
int main(){
	int a=100,s=1,d=0;
	while(a>=s){
	d=d+a;
	a=a-3;
	}
	cout<<d;
}

/**************************************************************
	Problem: 1053
	User: tonghuawei
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/