What will be the output of the following C++ code?

#include <iostream>
using namespace std;
int add(int first, int second)
{
    return first + second + 15;
}
int operation(int first, int second, int (*functocall)(int, int))
{
    return (*functocall)(first, second);
}
int main()
{
    int  a;
    int  (*plus)(int, int) = add;
    a = operation(15, 10, plus);
    cout << a;
    return 0;
}