View Compilation Error

0_0_20101471_7719.cpp: In function 'int main()':
0_0_20101471_7719.cpp:3:5: error: 'cin' is not a member of 'std'
     std::cin >> m;
     ^
0_0_20101471_7719.cpp:5:9: error: 'cin' is not a member of 'std'
         std::cin >> n;
         ^
0_0_20101471_7719.cpp:6:9: error: 'cout' is not a member of 'std'
         std::cout << (n + 1) * n / 2 << std::endl;
         ^
0_0_20101471_7719.cpp:6:41: error: 'endl' is not a member of 'std'
         std::cout << (n + 1) * n / 2 << std::endl;
                                         ^