View Compilation Error

0_0_37601361_27310.cpp: In function 'int main()':
0_0_37601361_27310.cpp:20:17: error: 'sqrt' was not declared in this scope
    sum += sqrt(2) * a;
                 ^
0_0_37601361_27310.cpp:21:24: error: 'pow' was not declared in this scope
    sum += sqrt(pow(a, 2) + pow(a + 1, 2));
                        ^
0_0_37601361_27310.cpp:23:16: error: 'sqrt' was not declared in this scope
   sum += sqrt(2) * p[1].first;
                ^