#include <stdio.h>
 
// Function declaration
int gcd(int a, int b);
 
int main() {
    int num1, num2, result;
 
    // Input two numbers
    printf("Enter two positive integers: ");
    scanf("%d %d", &num1, &num2);
 
    // Validate input
    if (num1 <= 0 || num2 <= 0) {
        printf("Please enter positive integers only.\n");
    } else {
        // Function call
        result = gcd(num1, num2);
        printf("GCD of %d and %d is %d\n", num1, num2, result);
    }
 
    return 0;
}
 
// Function definition using Euclidean algorithm
int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}