#include <stdio.h>

enum boolean {True = 1, False = 0}; 

int sum (int, int);
int difference (int, int);
int multiplication (int, int);

int main(void) {
	
	int op, num1, num2;
	
	printf ("Choose your operation\n");
	printf ("1. Sum\n");
	printf ("2. Number distance (always positive)\n");
	printf ("3. Multiplication\n");
	
	scanf("%d", &op);
	
	printf("Insert first number: ");
	scanf("%d", &num1);
	printf("\n");
	
	printf("Insert second number: ");
	scanf("%d", &num2);
	printf("\n");
	
	switch(op) {
		case 1:
			printf("The sum of %d and %d is: %d", num1, num2, sum(num1, num2));
			break;
		case 2:
			printf("The distance between %d and %d is: %d", num1, num2, difference(num1, num2));
			break;
		case 3:
			printf("The multiplication of %d and %d is: %d", num1, num2, multiplication(num1, num2));
			break;
	}
	
	// your code goes here
	return 0;
}

int sum (int num1, int num2) {
	return num1 + num2;
}

enum boolean is_bigger (int num1, int num2) {
	return num1 > num2;
}

int difference (int num1, int num2) {
	if (is_bigger(num1, num2)) {
		return num1 - num2;
	} else {
		return num2 - num1;
	}
}

int multiplication (int num1, int num2) {
	if (num2 == 0) {
		return num1;
	} else {
		return multiplication (num1 + num1, num2 - 1);
	}
}