#include <iostream>
#include <numeric>

struct iter {
  int n;
  iter( int x ): n(x){}
  int operator*(){ return (n%2)? n: 0; }
  bool operator==( const iter &i ){ return n == i.n; }
  bool operator!=( const iter &i ){ return !( *this == i ); }
  iter &operator++(){ ++n; return *this; }
};

int main(){
  int sum = std::accumulate( iter(0), iter(100), 0 );
  std::cout << sum << std::endl;
}