Why the answer is 3?

Question

#define square(x)(x*x)
int main()
{
int x, y=1;
x=square(y+1);
printf("%d",x);
return 0;
}
O/P :- 3

Answer 1

A macro definition will substitute the source code directly (the text itself). Therefore, the statement
x = square(y + 1); is actually
x = y + 1 * y + 1;
so, x is y + y + y, and the result is 3

Answer 2

Thank you, swim and Agent_1 , I got it. Thanks for help.