#include<bits/stdc++.h>
using namespace std;
int t,n,a[100005];
int main(){
    freopen("mod.in","r",stdin);
    freopen("mod.out","w",stdout);
    std::cin>>t;
    while(t--){
        std::cin>>n;
        int maxn=0,minn=114514,ans=0;
        for(int i=1;i<=n;i++){
            std::cin>>a[i];
            maxn=max(maxn,a[i]);
            minn=min(minn,a[i]);
        }
        if(minn==0||minn==1){
            cout<<maxn-minn<<endl;
            continue;
        }
        for(int i=1;i<=maxn;i++){
            int ma=0,mi=114514;
            for(int j=1;j<=n;j++){
                int op=a[j]%i;
                ma=max(ma,op);
                mi=min(mi,op);
            }
            ma=ma-mi;
            ans=max(ans,ma);
        }
        cout<<ans<<endl;
    }
    return 0;
}