GCD - Greatest Common Divisor using Functions in C

#include<stdio.h>

int main() {
    int a, b;
    printf("Enter 2 numbers:");
    scanf("%d%d", & a, & b);
    printf("Greatest Common Divisor is %d", gcd(a, b));

    return 0;
 }
int gcd(long a, long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}