#include<bits/stdc++.h> #define int long long using namespace std; int n,s,ans; int sum(int n){ int res=0; while(n){ res+=n%10; n/=10; } return res; } signed main(){ cin>>n>>s; if(s>=n){cout<<0;return 0;} for(int i=s;i<=n;i++){ if(i-sum(i)>=s){ cout<<n-i+1; return 0; } } cout<<0; return 0; }