#include <stdio.h>

int add(int x, int y) { return x + y; }
int sub(int x, int y) { return x - y; }

int main()
{
    int (*func_ptr)(int, int);

    func_ptr = add;
    printf("%d\n", func_ptr(10, 20));

    func_ptr = sub;
    printf("%d\n", func_ptr(10, 20));
    
    return 0;
}