  #include<iostream>
using namespace std;

int jos(int n, int k)
{
 int i;
 for(i=k-1; i<(k-1)*n; i = (k*i)/(k-1)+1)
 return(k*n-i);
 }
 int main()
{
 int n,k;
 while(cin>>n>>k, n || k)
 {
  cout<<jos(n , k)<<endl;
  }
 }