    //AYUSH VERMA       //*********************************************  *********************************       //***************/A **************************  ******   *********///*************       //**************//Y  ************************  ********   *******///**************       //*************///U   **********************  **********   **A**///***************       //************///*S*   ********************  ************   *M*///****************       //***********/////H     ******************  **************   R///*****************       //**********///*******   ****************  ****************  E//******************       //*********///*********   **************  ****************** V/*******************       //*************************************  *****************************************       #include<bits//stdc++.h>       #define till(condition) while(condition)       #define ull unsigned long long int       #define ll long long int       #define space printf(   )       #define nl printf(  n )       #define MOD 1000000007       using namespace std;       int main()       {           int t;           cin>>t;           till(t--)           {               int n;               cin>>n;               ll a[100001],want[100001];               ll max=0;               ll maxtest=0;               for(int i=0;i<n;i++)               {                   cin>>a[i];                   if(a[i]>maxtest)                   {                       maxtest=a[i];                   }               }               sort(a,a+n,greater<int>());               ll wantsum=0;               for(int i=0;i<n;i++)               {                   want[i]=(maxtest-a[i]);                   wantsum+=(want[i]);               }               for(int i=0;i<n;i++)               {                   ll temp=a[i],fill;                   ll tempwantsum=wantsum-want[i];                   if(i!=0)                   {                       fill=a[0];                   }                   else                   {                       fill=a[1];                   }                   ll subs=(n-1)*(temp-fill);                   if(subs>0)                   {                       tempwantsum-=(subs);                   }                                      // cout<< * <<temp;                   // nl;                   if(tempwantsum<=temp)                   {                       temp-=(tempwantsum);                       if(temp%(n-1)!=0)                       {                           ll ans=(n-1)-(temp%(n-1));                           if(ans>max)                           {                               max=ans;                           }                       }                   }                   else                   {                       if((tempwantsum-temp)>max)                       {                           max=(tempwantsum-temp);                       }                   }               //     cout<< ** <<max;               // nl;               }               cout<<max;               nl;                                            }                  }