source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.Map;
  
  public class Ds {
  	
  	static long lim;
  	
  	public static void main(String[] args) throws NumberFormatException, IOException {
  
  		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  		
  		String[] line = in.readLine().split("\\s+");
  		
  		long n = Long.parseLong(line[0]);
  		
  		lim = Long.parseLong(line[1]);
  	
  		
  		long pos = -1;
  		
  		for(int i=61; i>=0; i--) {
  			
  			long shift = (long) Math.pow(2, i);
  			
  			if(pos + shift - sumOfDigits(pos + shift) < lim) {
  				pos += shift;
  			}
  		}
  		
  		pos++;
  		
  		if(pos <= n && pos- sumOfDigits(pos) >= lim) {
  			System.out.println(n - pos + 1);
  		}
  		else {
  			System.out.println(0);
  		}
  		
  	}
  
  	private static long sumOfDigits(long d) {
  		
  		long sum = 0;
  		long num = d;
  		
  		while(num != 0) {
  			sum += (num%10);
  			num /= 10;
  		}
  		
  		return sum;
  	}
  }