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.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Random;
import java.util.StringTokenizer;

public class P {

	public static void main(String[] args) throws NumberFormatException, IOException {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int k = sc.nextInt();
		char[] s = sc.next().toCharArray();
		int sum = 0;
		PriorityQueue<Integer> pq = new PriorityQueue<Integer>();
		for (int i = 0; i < s.length; ++i) {
			sum += (s[i] - '0');
			pq.add(s[i] - '0');
		}
		int answer = 0;
		while (!pq.isEmpty()) {
			if (sum >= k)
				break;
			int curD = pq.remove();
			int diff = 9 - (curD);
			if (diff + sum <= k) {
				sum += diff;
				answer++;
			} else {
				answer++;
				break;
			}
		}
		out.println(answer);
		out.flush();
		out.close();
	}

	static class Scanner {
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

		public Scanner(String f) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(f));
		}

		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		public String nextLine() throws IOException {
			return br.readLine();
		}

		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		public boolean ready() throws IOException {
			return br.ready();
		}

		public int[] nextIntArray(int n) throws IOException {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}

		public int[] nextIntArray1(int n) throws IOException {
			int[] a = new int[n + 1];
			for (int i = 1; i <= n; i++)
				a[i] = nextInt();
			return a;
		}

		public int[] shuffle(int[] a, int n) {
			int[] b = new int[n];
			for (int i = 0; i < n; i++)
				b[i] = a[i];
			Random r = new Random();
			for (int i = 0; i < n; i++) {
				int j = i + r.nextInt(n - i);
				int t = b[i];
				b[i] = b[j];
				b[j] = t;
			}
			return b;
		}

		public int[] nextIntArraySorted(int n) throws IOException {
			int[] a = nextIntArray(n);
			a = shuffle(a, n);
			Arrays.sort(a);
			return a;
		}

		public long[] nextLongArray(int n) throws IOException {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}

		public long[] nextLongArray1(int n) throws IOException {
			long[] a = new long[n + 1];
			for (int i = 1; i <= n; i++)
				a[i] = nextLong();
			return a;
		}

		public long[] nextLongArraySorted(int n) throws IOException {
			long[] a = nextLongArray(n);
			Random r = new Random();
			for (int i = 0; i < n; i++) {
				int j = i + r.nextInt(n - i);
				long t = a[i];
				a[i] = a[j];
				a[j] = t;
			}
			Arrays.sort(a);
			return a;
		}
	}

}