What will be the output of the following C code?

#include <stdio.h>
int sub(int a, int b, int c)
{
    return a - b - c;
}
void main()
{
    int (*function_pointer)(int, int, int);
    function_pointer = ⊂
    printf("The difference of three numbers is:%d",
    (*function_pointer)(2, 3, 4));
}