View Compilation Error

1_867_1521_14309.cpp: In function 'int main()':
1_867_1521_14309.cpp:10:24: error: 'sqrt' was not declared in this scope
   int k=ceil(sqrt(1.0+n)-1.0);
                        ^
1_867_1521_14309.cpp:10:29: error: 'ceil' was not declared in this scope
   int k=ceil(sqrt(1.0+n)-1.0);
                             ^