View Compilation Error

0_0_32349173_28445.cpp: In function 'void Judge(const int&, const int&)':
0_0_32349173_28445.cpp:10:25: error: 'sqrt' was not declared in this scope
  for (i = 2; i <= sqrt(x); i++)
                         ^
0_0_32349173_28445.cpp:17:25: error: 'sqrt' was not declared in this scope
  for (i = 2; i <= sqrt(y); i++)
                         ^