#include <iostream>
#include <vector>
#include <fstream>
#include <math.h>
using namespace std;

int main(){
    string b;
    long long a;
    int re = 0,it = 0,kek = 0;
    cin >> a;
    cin>>b;
    vector<int>A;
    for(int i  = 0 ; i < b.size() ; i ++){
        A.push_back(int(b[i])-'0');
    }
    for (int i = 0 ; i < A.size() ; i ++ ) {
        kek += A[i];
    }
    if (kek  > a){
        cout<<0<<endl;
    }
    else{
        for ( int i = 0 ; i < 10 ; i++ ){
            for ( int j = 0 ; j < A.size() ; j++ ){
                if(A[j] == i){
                    kek =  kek - A[j] + 9;
                    A[j] = 9;
                    re+=1;

                }

                if (kek >= a){
                    it = 1;
                    break;
                }
            }


            if (it ==1){
                break;
            }
        }

        cout<<re;
    }

    return 0 ;
}