#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************

// cat batman lat matter cat matter cat



string a;

vector<string> consistency(int n){
	
	map<string, int> mp;

	stringstream ss(a);
	string temp;
	
	while(ss >> temp){
		mp[temp]++;
	}
	
	vector<string> ans;
	
	for(auto& t : mp){
		if(t.second >= 2){
			ans.push_back(t.first);
		}
	}
	
	return ans;
}















int practice(int n){


    return 0;
}




void solve() {

    getline(cin, a);

    int n = a.size();

    auto ans = consistency(n);
    for(auto& t : ans) cout << t << " ";  cout << endl;
    
    
}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}