View Compilation Error

0_0_17617805_15199.cpp: In function 'int main()':
0_0_17617805_15199.cpp:5:55: error: 'a' was not declared in this scope
     while(std::cin >> arr[0] >> arr[1]) { std::cout<< a[0] + a[1] << '\n'; }
                                                       ^