#include <iostream> 
using namespace std;   

int pt(int n, int m){  
  int i; 
  for(i = m-1 ; i < (m-1)*n ; i = (m*i) / (m-1)+1);
  return (m*n-i); 
  }   

int main(){     
  int n,m;  
  
  while( cin >> n >> m , n || m ) cout << pt(n,m) << endl;    
   
  return 0;
 }