#include <bits/stdc++.h> using namespace std; #define int long long int n,s,x,sum,ans,k,s2; signed main(){ cin >> n >> s; s2=s; while (s2>0){ k ++; s2 /= 10; } for (int i=s; i<=min(s+k*10,n); i++){ x=i; sum=0; while (x>0){ sum += x%10; x /= 10; } if (i-sum>=s) ans ++; } if (n>s+k*10) ans += n-s-k*10; cout << ans; return 0; }