#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e18 + 7;
string s, t;
long long stn(string a) {
  reverse(a.begin(), a.end());
  long long res = 0;
  for (long long i = 0; i < a.size(); i++) {
    long long c = a[i] - '0';
    res += pow(10, i) * c;
  }
  return res;
}
int32_t main() {
  cin >> s;
  long long x = s[0] + 1 - '0';
  while (x) {
    t += (x % 10) + '0';
    x /= 10;
  }
  reverse(t.begin(), t.end());
  for (long long i = 1; i < s.size(); i++) t += '0';
  cout << stn(t) - stn(s);
}
