Problem:
Score : 100 points

Problem Statement

We will buy a product for N yen (the currency of Japan) at a shop.

If we use only 1000-yen bills to pay the price, how much change will we receive?

Assume we use the minimum number of bills required.

Constraints

1 \leq N \leq 10000

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the amount of change as an integer.

Sample Input 1

1900

Sample Output 1

100

We will use two 1000-yen bills to pay the price and receive 100 yen in change.

Sample Input 2

3000

Sample Output 2

0

We can pay the exact price.

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
#include <stdio.h>
#define ll long long
#define fr(i,p,n) for(int i=p;i<n;i++)
#define fr1(i,p,n) for(int i=p;i>=n;i--)
#define FAST ios::sync_with_stdio(0);
#define sz(v) (ll)v.size()
#define pb push_back
#define ff first
#define ss second
#define all(v) v.begin(),v.end()
#define PI 3.14159265358979323846
#define mod 1000000007
#define mod1 998244353
#define precise cout << std::setprecision(12) << std::fixed;
#define endl "\n"
using namespace std;

int main()
{
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);
    FAST
    int t=1;
    //cin>>t;
    while(t--)
    {
        int n;
        cin>>n;
        int ans=n%1000;
        cout<<1000-ans<<endl;    
    }
    return 0;
}