#include <iostream>
#include <cmath>
using namespace std;
typedef long long ll;
int main() {
ll n;
cin >> n;
bool flag = 1;
if (n == 0)
return cout << 0, 0;
if (n < 10)
return cout << 10 - n, 0;
int scs = 1;
ll m = n;
while (m > 9) {
if (m % 10 != 0)
flag = 0;
m /= 10;
scs++;
}
if (flag)
return cout << 0, 0;
ll mul = pow(10,scs - 1);
cout << (n / mul + 1)*mul - n;
return 0;
}