#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const long long linf = 0x3f3f3f3fLL;
int a[2010];
int main() {
  int n;
  scanf("%d", &n);
  int aux = n;
  int resp = 1;
  while (aux) {
    if (aux == n) {
      aux /= 10;
      continue;
    }
    aux /= 10;
    resp *= 10;
  }
  aux = n;
  int fact = 1;
  while (aux >= 10) {
    resp -= fact * (aux % 10);
    aux /= 10;
    fact *= 10;
  }
  if (n < 10)
    puts("1");
  else
    printf("%d\n", resp);
  return 0;
}
