View Compilation Error

0_0_2172208_29982.cpp: In function `int main()':
0_0_2172208_29982.cpp:10: error: no match for 'operator>>' in '(&std::cout)->std::basic_ostream<_CharT, _Traits>::operator<< [with _CharT = char, _Traits = std::char_traits<char>](((n - 1) * n)) >> 1'