#include <iostream>
#include <string>
using namespace std;
double add(double x, double y);
double calculate(double a, double b, double (*pf)(double, double));
int main() {
double q = calculate(2.5, 10.4, add);
cout << q << endl;
return 0;
}
double add(double x, double y) {
return x + y;
}
double calculate(double a, double b, double (*pf)(double, double)) {
return (*pf)(a, b);
}