Some natural number was written on the board. Its sum of digits was not less than k. But you were distracted a bit, and someone changed this number to n, replacing some digits with others. It's known that the length of the number didn't change.

You have to find the minimum number of digits in which these two numbers can differ.

Input

The first line contains integer k (1 ≤ k ≤ 109).

The second line contains integer n (1 ≤ n < 10100000).

There are no leading zeros in n. It's guaranteed that this situation is possible.

Output

Print the minimum number of digits in which the initial number and n can differ.

Examples

Input

3
11


Output

1


Input

3
99


Output

0

Note

In the first example, the initial number could be 12.

In the second example the sum of the digits of n is not less than k. The initial number could be equal to n.
												import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;
								public class Solution1 implements Runnable
								{
									static final long MAX = 1000000007L;
									static class InputReader
									{
										private InputStream stream;
										private byte[] buf = new byte[1024];
										private int curChar;
										private int numChars;
										private SpaceCharFilter filter;
										private BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
								 
										public InputReader(InputStream stream)
										{
											this.stream = stream;
										}
										
										public int read()
										{
											if (numChars==-1) 
												throw new InputMismatchException();
											
											if (curChar >= numChars)
											{
												curChar = 0;
												try 
												{
													numChars = stream.read(buf);
												}
												catch (IOException e)
												{
													throw new InputMismatchException();
												}
												
												if(numChars <= 0)				
													return -1;
											}
											return buf[curChar++];
										}
									 
										public String nextLine()
										{
											String str = "";
								            try
								            {
								                str = br.readLine();
								            }
								            catch (IOException e)
								            {
								                e.printStackTrace();
								            }
								            return str;
										}
										public int nextInt()
										{
											int c = read();
											
											while(isSpaceChar(c)) 
												c = read();
											
											int sgn = 1;
											
											if (c == '-') 
											{
												sgn = -1;
												c = read();
											}
											
											int res = 0;
											do 
											{
												if(c<'0'||c>'9') 
													throw new InputMismatchException();
												res *= 10;
												res += c - '0';
												c = read();
											}
											while (!isSpaceChar(c)); 
											
											return res * sgn;
										}
										
										public long nextLong() 
										{
											int c = read();
											while (isSpaceChar(c))
												c = read();
											int sgn = 1;
											if (c == '-') 
											{
												sgn = -1;
												c = read();
											}
											long res = 0;
											
											do 
											{
												if (c < '0' || c > '9')
													throw new InputMismatchException();
												res *= 10;
												res += c - '0';
												c = read();
											}
											while (!isSpaceChar(c));
												return res * sgn;
										}
										
										public double nextDouble() 
										{
											int c = read();
											while (isSpaceChar(c))
												c = read();
											int sgn = 1;
											if (c == '-') 
											{
												sgn = -1;
												c = read();
											}
											double res = 0;
											while (!isSpaceChar(c) && c != '.') 
											{
												if (c == 'e' || c == 'E')
													return res * Math.pow(10, nextInt());
												if (c < '0' || c > '9')
													throw new InputMismatchException();
												res *= 10;
												res += c - '0';
												c = read();
											}
											if (c == '.') 
											{
												c = read();
												double m = 1;
												while (!isSpaceChar(c)) 
												{
													if (c == 'e' || c == 'E')
														return res * Math.pow(10, nextInt());
													if (c < '0' || c > '9')
														throw new InputMismatchException();
													m /= 10;
													res += (c - '0') * m;
													c = read();
												}
											}
											return res * sgn;
										}
										
										public String readString() 
										{
											int c = read();
											while (isSpaceChar(c))
												c = read();
											StringBuilder res = new StringBuilder();
											do 
											{
												res.appendCodePoint(c);
												c = read();
											} 
											while (!isSpaceChar(c));
											
											return res.toString();
										}
									 
										public boolean isSpaceChar(int c) 
										{
											if (filter != null)
												return filter.isSpaceChar(c);
											return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
										}
									 
										public String next() 
										{
											return readString();
										}
										
										public interface SpaceCharFilter 
										{
											public boolean isSpaceChar(int ch);
										}
									}
								 	
									public static void main(String args[]) throws Exception
									{
										new Thread(null, new Solution1(),"Solution1",1<<26).start();
									}
									
								    // method to return LCM of two numbers
								   
									public void run()
									{
										InputReader sc= new InputReader(System.in);
										PrintWriter w= new PrintWriter(System.out);
										int n = sc.nextInt();
										String s=  sc.next();
										int sum = sum(s);
										if(sum < n){
											int diff = n - sum;
											char[] ch = s.toCharArray();
											Arrays.sort(ch);
											int count = 0;
											for(int i = 0;i < ch.length;i++){
												if(diff <= 0){
													break;
												}
												diff = diff - 9 + Integer.parseInt(ch[i] + "");
												count++;
											}
											w.println(count);
										}else{
											w.println(0);
										}
										w.close();
									}
									int sum(String s){
										int sum = 0;
										for(int i = 0;i < s.length();i++){
											sum += Integer.parseInt(s.charAt(i) + "");
										}
										return sum;
									}
									static class Pair implements Comparable<Pair>{
										int a;
										int b;
										Pair(){}
										Pair(int a,int b){
											this.a = a;
											this.b = b;
											
										}
										public int compareTo(Pair p){
											return Integer.compare(this.b,p.b);
										}
									}
					}
