import java.math.*;  
import java.util.*;  
public class Main {  
  
 
 public static void main(String[] args) {  
  // TODO Auto-generated method stub  
  BigInteger a,b;  
  Scanner cin = new Scanner(System.in);  
    
  while(cin.hasNext()){  
   a = cin.nextBigInteger();  
   b = cin.nextBigInteger();  
            BigInteger result=a.mod(b);
   System.out.println(result);  
  }  
 }  
  
}