#include <bits/stdc++.h>
using namespace std;
const long long N = (long long)1e6 + 5;
const long long mod = (long long)1e9 + 7;
int n;
int s(int x) {
  int cnt = 0;
  while (x > 0) {
    cnt++;
    x /= 10;
  }
  return cnt;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  int sz = s(n), res = 1;
  for (int i = 2; i <= sz; i++) res *= 10;
  long long k = n / res + 1;
  for (int i = 2; i <= sz; i++) k *= 10;
  cout << k - n << endl;
  return 0;
}
