Example:

#include <stdio.h>

#define MAX_GF 100

int main(){
	
	printf("Hello\n");
	#if MAX_GF>=50
		printf("Wau, you may have more than 50 girlfriends\n");
		printf("Code for more than 50 GFs\n");
	#endif
	printf("Bye!\n");
	
	return 0;
}

Output

    Hello
    Wau, you may have more than 50 girlfriends
    Code for more than 50 GFs
    Bye!