#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);

}