#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll =  long long ;
using P = pair<int,int> ;
using pll = pair<ll,ll>;
constexpr int INF = 1e9;
constexpr ll LINF = 1e18;
constexpr int MOD = 1000000007;

int main(){
    ll n;
    cin >> n;
    ll ans = 0;
    for(ll i=1;i*i<=n;i++){
        if(n%i == 0 && ((n/i)%2 ==0 || (n-1)%2 ==0)){
            ans += i;
        }

        if(i*i == n) break;

        if(n%i ==0 && (i%2==0 || (n-1)%2==0)){
            ans += n/i;
        }
    }
    cout << ans << endl;
    return 0;
}