#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
// #include <algorithm>
// #include <queue>
// #include <map>
// #include <iostream>
// #include <string>
// #include <set>
#define endl '\n'
// #define int long long

using namespace std;
using namespace __gnu_pbds;

using LL = long long; 
using PII = pair<int, int>;
using i128 = __int128_t;
using ULL = unsigned long long;
using Tree = tree<PII, null_type, less<PII>, rb_tree_tag, tree_order_statistics_node_update>;

constexpr int INF = 0x3f3f3f3f, MOD = 1e9 + 7, N = 1e6 + 5, M = 1e6 + 5;
constexpr LL LINF = 0x3f3f3f3f3f3f3f3f;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void solve()    
{   
    string s;
    cin >> s;
    int n = s.size();
    vector<int> a;
    for(int i = 0; i < n; i ++) {
        if(!a.empty() and a.back() == s[i] - '0') continue;
        a.push_back(s[i] - '0');
    }

    if(a.size() < 2) {
        cout << a[0] << endl;
    } else if(a.size() % 2 == 0) {
        cout << a[0] << a[1] << endl;
    } else {
        cout << a[0] << a[1] << a.back() << endl;
    }
}

signed main()
{
    // (.*)   "$1"
    // freopen("park.in", "r", stdin);
    // freopen("park.out", "w", stdout);
	// cout << fixed << setprecision(2);
    // srand(NULL);
    ios::sync_with_stdio(false), cin.tie(nullptr);
    int T = 1;
	// cin >> T;

    while(T -- )
        solve();

    // fclose(stdin);
    // fclose(stdout);
    return 0;
}