Function Pointer apply

#include <iostream>
#include <string>
using namespace std;

int square(int x) { return x * x; }
int cube(int x) { return x * x * x; }

// your code here: define apply(int, function pointer)
void apply(int x, int (*op)(int)) {
    cout << op(x) << "\n";
}

int main() {
   int n;
   string opName;
   cin >> n >> opName;
   if (opName == "square") {
       apply(n, square);
   } else if (opName == "cube") {
       apply(n, cube);
   }
   return 0;
}