//Romene                           
                             

                                #include<bits/stdc++.h>
                                
                                #include<string>
                                
                                #include <sstream>
                                using namespace std;
             
                                #define ll long long
                                #define ld long double
                                #define pb push_back
                                #define pf push_front
                                #define f first
                                #define s second
                                #define all(c)  c.begin(), c.end()
                                #define ulli unsigned long long int
                                #define lli long long int
                                #define llv vector< ll >
                                #define llc vector< char >
                                #define lls vector< string >
                                #define llb vector< bool >
                                #define mp make_pair
                                #define endl "\n"
                                #define debg cout<<"HI"<<endl;
                                #define ins insert
                                #define foo(i,n) for(ll i = 0;i<n;i++)
                                #define foa(i,a) for(ll i = 0;i<a.size();i++)
                                #define foe(i,a,b) for(ll i = a;i<=b;i++)
                                #define max3(a,b,c) max(max(a,b),c)
                                #define min3(a,b,c) min(min(a,b),c)
                                #define INF 2147483647
                                #define len length
                                #define sp setprecision(16)
                                #define mod 1000000007
                                 
                                lli powr(ll a,ll b){   /*power(a,b) by modular exponentiation*/
                                  if(b==0){
                                    return 1;
                                  }
                                  if(b%2==0){
                                    return powr(((a%mod)*(a%mod))%mod,b/2);
                                  }
                                  else{
                                    if(b==1){
                                      return a;
                                    }
                                    else{
                                      return (a*powr(((a%mod)*(a%mod)%mod),(b-1)/2))%mod;
                                    }
                                  }
                                }
                                 ll gcd1(ll a,ll b){
                                  if(a==0)
                                    return b;
                                  else{
                                    return gcd1( b%a, a);
                                  }
                                 }
                                 ll lcm(ll a, ll b)  
                              {  
                                 return (a*b)/gcd1(a, b);  
                              }  
                                 ll mod1(ll a){
                                  if(a<0)
                                    return -1*a;
                                  else{
                                    return a;
                                  }
                                 }
                              
                                 bool isPrime(int num){
                               
                                for(int i = 2; i*i <= (num); i++) {
                                   if(num % i == 0) {
                                      return false;
                                      break;
                                   }
                                }
                                return true;
                            }
                           
                                      
                                int main(){
                                   /* #ifndef ONLINE_JUDGE
                                    freopen("input.txt", "r", stdin);
                                    freopen("output.in", "w", stdout);
                                    #endif*/
                                    ios::sync_with_stdio(0);
                                    cin.tie(0); cout.tie(0);
                                
                                 
                                     int f1;
                                     f1=1;
                                     
                                                           
                                    
                                 for(int y2=0;y2<f1;y2++){
                              ll n;
                              cin >> n;
                              if(n%1000==0)cout << 0;
                              else{
                                cout << 1000-n%1000;
                              }
                               
                           }


                               




                                           
                                    cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";
                                
                              
                                
                                                                                       
                                                   
                                 }
                                

Measured memory_bytes: 3800