#include <bits/stdc++.h>
using namespace std;
long long q=100,h;
int main(){
     while(q>=1){
     	h=h+q;
     	q=q-3;
     }
     cout<<h;
}
/**************************************************************
	Problem: 1053
	User: chenyichuen
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/