21-9-18 C.cpp

#include<bits/stdc++.h>
using namespace std;
int gcd(int a,int b)
{
    if(a==0)
        return b;
    return gcd(b%a,a);
}
int find_gcd(int a[],int n,int start)
{
    int result = a[start];
    for(int i = start ;i<n;i++)
        result = gcd(a[start],a[i]);

    return result;
}
int main()
{
    int n;
    cin>>n;
    int a[n],result[n];
    for(int i = 0;i<n;i++)
        cin>>a[i];
    sort(a,a+n);
    for(int i = 0; i < n - 1 ; i++)
    {
        result[i]=find_gcd(a,n,i);
   //     cout<<result[i]<<endl;
    }
    int res = 0, k,c = 0;
    for(int i = 0 ;i< n-1;i++)
    {
        if(result[i]>result[0])
        {
            res = result[i];
            k=i;
            c=1;
        }
    }
if(c)
    cout<<k<<endl;
else
    cout<<"-1"<<endl;
return 0;
}