View Compilation Error

0_0_30989221_16822.cpp: In function 'int main()':
0_0_30989221_16822.cpp:12:21: error: 'n' was not declared in this scope
         cout<<pow(3,n)<<endl;
                     ^
0_0_30989221_16822.cpp:12:22: error: 'pow' was not declared in this scope
         cout<<pow(3,n)<<endl;
                      ^