View Compilation Error

0_0_38105656_23778.cpp: In function 'void count(int)':
0_0_38105656_23778.cpp:29:54: error: 'pow' was not declared in this scope
     double in=po(5,3*l),os=po(2,7*l),ans=1-(pow(5,3*l)/pow(2,7*l));
                                                      ^