#include <bits/stdc++.h>
using namespace std;
int main() {
  string num;
  cin >> num;
  long long int num1 = stoi(num);
  if (num[0] != '9') {
    num[0]++;
    for (int i = 1; i < num.length(); ++i) {
      num[i] = '0';
    }
  } else {
    string num2 = '1' + num;
    for (int i = 1; i < num2.length(); ++i) {
      num2[i] = '0';
    }
    num = num2;
  }
  long long int num22 = stoi(num);
  cout << num22 - num1 << endl;
  return 0;
}
