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

/**************************************************************
	Problem: 1053
	User: fzy001
	Language: C++
	Result: Accepted
	Time:5 ms
	Memory:2072 kb
****************************************************************/