#include <bits/stdc++.h> using namespace std; const int N=1e5+9; long long n,s,ans; int main(){ cin>>n>>s; for(long long i=999999999999999999;i>=9;i/=10){ if(s>=i)for(long long j=9;j>=1;j--)if(s>j*i)ans+=j,s-=j*i; ans*=10; } ans+=9; cout<<max(1LL*0,n-ans); return 0; }