#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (a < b) {
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
  }
  if (b == 0) return a;
  long long t;
  while (b) {
    t = b;
    b = a % b;
    a = t;
  }
  return a;
}
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
long long powermod(long long _a, long long _b, long long _m = 1000000007) {
  long long _r = 1;
  while (_b) {
    if (_b % 2 == 1) _r = (_r * _a) % _m;
    _b /= 2;
    _a = (_a * _a) % _m;
  }
  return _r;
}
long long power(long long _a, long long _b) {
  long long _r = 1;
  while (_b) {
    if (_b % 2 == 1) _r = (_r * _a);
    _b /= 2;
    _a = (_a * _a);
  }
  return _r;
}
int main() {
  std::ios_base::sync_with_stdio(false);
  int w = 0;
  if (w) {
    freopen("C:/Users/gold/Desktop/sublime IO/input.txt", "r", stdin);
    freopen("C:/Users/gold/Desktop/sublime IO/output.txt", "w", stdout);
  }
  long long int n;
  cin >> n;
  if (n < 10) {
    cout << "1";
    return 0;
  }
  int p[200005];
  p[0] = 10;
  int j = 1;
  for (int i = 1; i < 100000; i++) {
    p[i] = p[i - 1] + 10 * j;
    if (i % 9 == 0) j = j * 10;
  }
  int i;
  for (i = 0; i < 100000; i++) {
    if (p[i] >= n) break;
  }
  if (p[i] == n)
    cout << p[i + 1] - n << endl;
  else
    cout << p[i] - n << endl;
  return 0;
}
