        #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;
    }
}