View Compilation Error

0_0_38650405_29666.cpp: In function 'int countMethods(int, const std::vector<std::pair<int, int> >&)':
0_0_38650405_29666.cpp:19:24: error: 'pow' was not declared in this scope
     int totalMethods = pow(2, n) - nodes.size(); // 2^n - number of nodes
                        ^~~
0_0_38650405_29666.cpp:19:24: note: suggested alternative: 'putw'
     int totalMethods = pow(2, n) - nodes.size(); // 2^n - number of nodes
                        ^~~
                        putw