#include "iostream"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define ll long long
#define endl ("\n")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ft (frist)
#define sd (second)
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const long long INF = 1e18+1LL;
const int inf = 1e9+1e8;
const int N=1e5+100;
const ll mod=1e9+7;

///BBBB

char s[N];
int k,vis[15];
int main(){
    cin>>k>>s+1;
    int ls=strlen(s+1);
    ll t=0;
    for(int i=1; i<=ls; ++i){
        t+=s[i]-‘0‘;
        vis[s[i]-‘0‘]++;
    }
    ll c=k-t,ans=0;
    if(c<=0){
        cout<<"0\n";
        return 0;
    }
    for(int i=0; i<=9; ++i){
        if(vis[i]*(9-i) >= c){
            ans+=c/(9-i);
            if(c%(9-i)!=0) ans++;
            break;
        }
        else{
            ans+=vis[i];
            c-=vis[i]*(9-i);
        }
    }
    cout<<ans<<"\n";
    return 0;
}