#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define ll long long
#define ull unsigned long long
#define pll pair<ll,ll>
#define pb push_back
#define emb emplace_back
#define lg(x) __lg(x)
#define all(s) s.begin(),s.end()
#define name "test"
#define Mask(i) (1LL<<i)
#define testbit(mask, i) ((mask >> i) & 1LL)
#define onBit(mask, i) (mask | (1LL << i))
#define offBit(mask, i) (mask & ~(1LL << i))
#define flipBit(mask, i) (mask ^ (1LL << i))
#define showbit(mask, x) bitset<x>(mask)
const ll mod = 1e9 + 7;

void add(ll &a, ll b){
     if((a += b) >= mod) a -= mod;
}


const ll inf = 1e18;
const ll lim = 1e7 + 5;
const ll N = 2e5 + 5;

int main()
{
     ios_base::sync_with_stdio(0);
     cout.tie(0);cin.tie(0);
     if(fopen(name".inp","r")){
          freopen(name".inp","r",stdin);
          freopen(name".out","w",stdout);
     }

     ll n; cin >> n;
     for(int i = 9 * 12; i >= 1; i--){
          ll m = n - i;
          if(m <= 0) continue;

          int sum = 0;
          while(m){
               sum += m % 10;
               m /= 10;
          }

          if(sum == i){
               cout << n - i;
               return 0;
          }
     }
     cout << 0;


}