1_gcd.c

#include <stdio.h>

int hcf(int n1, int n2)
{
    if (n2 != 0)
        return hcf(n2, n1 % n2);
    else
        return n1;
}

int main()
{
    int n1, n2;
    printf("Enter two positive integers: ");
    scanf("%d %d", &n1, &n2);
    printf("GCD of %d and %d is %d.", n1, n2, hcf(n1, n2));
    return 0;
}