View Compilation Error

0_0_38614971_14599.cpp: In function 'int main()':
0_0_38614971_14599.cpp:17:20: error: 'sqrt' was not declared in this scope
   int m=(int)(k*(1+sqrt(5))/2.0)
                    ^~~~
0_0_38614971_14599.cpp:17:20: note: suggested alternative: 'qsort'
   int m=(int)(k*(1+sqrt(5))/2.0)
                    ^~~~
                    qsort