#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long b) {
  if (b == 0) return 1;
  if (b % 2) return power(a, b / 2) * power(a, b / 2) * a;
  return power(a, b / 2) * power(a, b / 2);
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  vector<long long> lucky;
  for (long long i = 1; i < 10; i++)
    for (long long j = 0; j < 10; j++) lucky.push_back(i * power(10, j));
  sort(lucky.begin(), lucky.end());
  long long x = lower_bound(lucky.begin(), lucky.end(), n) - lucky.begin();
  if (lucky[x] == n) x++;
  cout << lucky[x] - n;
  return 0;
}
