#include <bits/stdc++.h>
using namespace std;
int main(){
    int n=100,s=0,i=1;
    while(i<=n){
        s=s+i;
        i=i+3;
    }
    cout<<s;
    return 0;
}                             
/**************************************************************
	Problem: 1053
	User: wangyousi
	Language: C++
	Result: Accepted
	Time:5 ms
	Memory:2072 kb
****************************************************************/