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