BTCD14A-Game of Pips

Game of Pips

below given code is for btcd14a spoj or Game of Pips spoj

#include <stdio.h>
#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;
long long GCD(long long a,long long b)
{
 return b==0?a:GCD(b,a%b);
}
int main()
{
 int n;
 scanf("%d",&n);
 long long a[n+9],k;
 scanf("%lld",&a[0]);
 int i;
 k=a[0];
 for(i=1;i<n;i++)
 {
  scanf("%lld",&a[i]);
  k=GCD(k,a[i]);
 }
 if(k%2==0)
 {
  while(k%2!=1)
   k=k/2;
  printf("%lld\n",k);
 }
 else 
  printf("%lld\n",k);
 return 0;
}