#include<bits/stdc++.h>
using namespace std;
int main(){
	int n=100,s=0;
	while(n>=0){
		s=s+n;
		n=n-4;
	}
	cout<<s;
}
/**************************************************************
	Problem: 1053
	User: zengyixuan
	Language: C++
	Result: Wrong Answer
****************************************************************/