include <bits/stdc++.h>

using namespace std;
string tao(char a, int l){
string s ="";
for(int i =0;i<l;i++){ s+= a; } return s; } int main(){ ios_base::sync_with_stdio(false); cout.tie(nullptr);cin.tie(nullptr); string s; cin>>s;
string k = tao(s[0],s.length());
if(k<s)
k = tao(char(int(s[0]-'0')+1+'0'),s.length());
cout<<stoll(k) - stoll(s);
return 0;
}