View Compilation Error

0_0_38515035_31652.cpp: In function 'int main()':
0_0_38515035_31652.cpp:4:12: error: 'cin' was not declared in this scope
     while (cin >> a >> b)
            ^
0_0_38515035_31652.cpp:6:9: error: 'cout' was not declared in this scope
         cout << (a + b)*(b - a + 1)/2 << endl;
         ^
0_0_38515035_31652.cpp:6:42: error: 'endl' was not declared in this scope
         cout << (a + b)*(b - a + 1)/2 << endl;
                                          ^