Optimizing for loop time complexity

How to reduce time complexity for this??

          #include<iostream>
     using namespace std;
   string choc(long long n)
  {
  long long m=n;
string p;
for(long long i=1;i<=n;i++)
{
if(m>=i)
{
    m=m-i;
    if(i%2!=0)
    {
        p='A';
    }
    else if(i%2==0)
    {
        p='B';
    }
}
else
{
    break;
}
}
return p;
  }

 int main()
 {
   long long t,n;
   cin>>t;
    while(t--)
   {
    cin>>n;
    cout<<choc(n)<<endl;
    }
}