#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()
#define len(x) (int)x.length()
#define ac(x, i) get<i>(x)
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define pll pair<ll ,ll>
#define pli pair<ll, int>
#define ff first
#define ss second
#define trace(x)    cerr << #x << ": " << x << "\n"
#define trav0(a, n) cerr << #a << "[" << n <<  "] = ["; for (int i = 0; i < n; i++) cerr << a[i] << ", "; cerr << "]\n"
#define trav1(a, n) cerr << #a << "[" << n <<  "] = ["; for (int i = 1; i <= n; i++) cerr << a[i] << ", "; cerr << "]\n"
#define trap0(a, n) cerr << #a << "[" << n <<  "] = ["; for (int i = 0; i < n; i++) cerr << "(" << a[i].ff << ", " << a[i].ss << "), "; cerr << "]\n"
#define trap1(a, n) cerr << #a << "[" << n <<  "] = ["; for (int i = 1; i <= n; i++) cerr << "(" << a[i].ff << ", " << a[i].ss << "), "; cerr << "]\n"
#define travMap(a)  cerr << #a << "[" << sz(a) <<  "] = ["; for (auto i : a) cerr << "(" << i.ff << ", " << i.ss << "), "; cerr << "]\n"
#define traverse(a) cerr << #a << "[" << sz(a) <<  "] = ["; for (auto i : a) cerr << i << ", "; cerr << "]\n"
#define random_permute(x) shuffle(all(x), mt)
#define FOR(a, b, c) for (int(a) = (b); (a) < (c); ++(a)) 
#define FORN(a, b, c) for (int(a) = (b); (a) <= (c); ++(a)) 
#define FORD(a, b, c) for (int(a) = (b); (a) >= (c); --(a)) 
#define FORSQ(a, b, c) for (int(a) = (b); (a) * (a) <= (c); ++(a)) 
#define FORC(a, b, c) for (char(a) = (b); (a) <= (c); ++(a)) 
#define FOREACH(a, b) for (auto&(a) : (b)) 
#define REP(i, n) FOR(i, 0, n) 
#define REPN(i, n) FORN(i, 1, n) 

typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long int ull;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vii;
typedef vector<pll> vll;
typedef vector<bool> vb;
typedef vector<string> vs;
const int infi = 1e9;
const ll infl = 1e18;
const int MOD = 1e9 + 7;
//template <typename Map> bool map_compare (Map const &lhs, Map const &rhs) { return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());}
//auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
//mt19937 mt(seed);
//int randint(int p = MOD) { return mt() % p;}
//ll randlong(ll p = infl) { return mt() % p;}
ll log_2 (ll n) { return (n > 1ll)? 1ll + log_2(n/2): 0ll;}
inline void add(ll&a, ll b) {a += b; if (a >= MOD) a -= MOD;}
inline void sub(ll&a, ll b) {a -= b; if (a < 0) a += MOD;}

/* CONVERT A INTEGER TO A STRING */

inline string IntToString(ll a) 
{ 
    char x[100]; 
    sprintf(x, "%lld", a); 
    string s = x; 
    return s; 
} 


/* CONVERT A STRING TO AN INTEGER */
  
inline ll StringToInt(string a) 
{ 
    char x[100]; 
    ll res; 
    strcpy(x, a.c_str()); 
    sscanf(x, "%lld", &res); 
    return res; 
} 


/* TO ENTER A STRING AS A CHARACTER ARRAY AND THEN CONVERT IT TO A SINGLE STRING */

  
inline string GetString(void) 
{ 
    char x[1000005]; 
    scanf("%s", x); 
    string s = x; 
    return s; 
} 

/* CONVERT A STRING TO UPPER CASE */

  
inline string uppercase(string s) 
{ 
    int n = sz(s); 
    REP(i, n) 
    if (s[i] >= 'a' && s[i] <= 'z') 
        s[i] = s[i] - 'a' + 'A'; 
    return s; 
} 
  
/* CONVERT A STRING TO LOWER CASE */
  
inline string lowercase(string s) 
{ 
    int n = sz(s); 
    REP(i, n) 
    if (s[i] >= 'A' && s[i] <= 'Z') 
        s[i] = s[i] - 'A' + 'a'; 
    return s; 
} 

  
inline void OPEN(string s) 
{ 
#ifndef TESTING 
    freopen((s + ".in").c_str(), "r", stdin); 
    freopen((s + ".out").c_str(), "w", stdout); 
#endif 
} 

/* TO DISPLAY AN ARRAY ON THE SCREEN */

void showarr(ll arr[],ll n)
{
	int i;
	for(i=0;i<n;i++)
	{
		cout<<arr[i]<<" ";
	}
	cout<<endl;
  }  

/*TO DISPLAY A VECTOR OF INTERGERS */


void showvec(vector <ll> v)
{
	int i;
	for(i=0;i<v.size();i++)
	{
		cout<<v[i]<<" ";
	}
	cout<<endl;
  }  
  
/* TO CHECK IF A STRING IS PALINDROME*/  
  
  int isPalindrome(string str) 
{ 
    int l = 0; 
    int h = str.length() - 1; 
  while (h > l) 
    { 
        if (str[l++] != str[h--] ) 
        { 
            return 0; 
        } 
    } 
    return 1;
} 

/*   DISPLAY A VECTOR OF PAIRS */

  void showvecpair(vll v)
  {
  	for(int i=0;i<sz(v);i++)
  	{
  		cout<<v[i].first<<" "<<v[i].second<<endl;
	  }
  }
 
/*   TO SORT A VECTOR OF PAIRS VIA SECOND ELEMENT.........CHECK NOTEPAD */  
  
bool sortbysec(const pll &a, 
              const pll &b) 
{ 
    return (a.second < b.second); 
}   

/*   TO PRINT BINARY REPRESENTATION OF ANY NUMBER */  

void bin(unsigned n) 
{ 
    unsigned i; 
    for (i = 1 << 31; i > 0; i = i / 2) 
        (n & i)? printf("1"): printf("0"); 
}     

/*   TO COUNT NUMBER OF SET BITS IN BINARY REPRESENTATION OF ANY NUMBER */  

ll cntset(ll n)
{
	bitset<64> b1(n);  //represents in 64 bit format
	return b1.count();
}  
  


// end of Sektor_jr template v2.0.3 (BETA) 
  
  
  
  
  
  
void solve()
{
	long long int l,t,a,b,k,m,n,y,i,j,max=INT_MIN,ctr=0,cnt=0,x,ctr1=0,p=1;
	cin>>n;
	x=n/1000;
	if(n%1000==0)
	{
		cout<<"0"<<endl;
	}
	else
	{
		y=1000*(x+1)-n;
		cout<<y<<endl;
	}
	
}




int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int i,T;
   
   	T=1;
	//cin>>T;
    
    for(i=1;i<=T;i++)
    {
    	solve();
	}
    return 0;
    
    
}

Measured memory_bytes: 3640