#include <bits/stdc++.h> #define int long long using namespace std; int n,s; int ans=0; signed main(){ // freopen("num.in","r",stdin); // freopen("num.out","w",stdout); cin>>n>>s; if(n<=s){ cout<<"0"; return 0; } for(int i=s+9;i<=min(n,s+9*18);i++){ int sum=0; int a=i; while(a!=0){ sum+=a%10; a/=10; } // cout<<sum<<endl; if(i-sum>=s)ans++; } if(n-(s+9*18)>=0){ ans+=n-(s+9*18); } cout<<ans<<endl; return 0; }