题解

#include<bits/stdc++.h>
#include<set>
using namespace std;
const int N = 2e5+9;
int a[N],hou[1009];
int main()
{
int T;
cin >> T;
while(T--)
{
int n;
cin >> n;
memset(hou,0,sizeof(hou));
for(int i = 1;i <= n;i++)
{
cin >> a[i];
hou[a[i]] = i;
}
int ans = -1;
for(int i = 0;i <= 1000;i++)
{
for(int j = 0;j <= 1000;j++)
{
if(__gcd(i,j) == 1 && hou[i] && hou[j]) ans = max(hou[i] +hou[j],ans);
}
}
cout << ans << endl;
}
return 0;
}