  #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;
  }
 }