#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define eb emplace_back
//mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define mod 998244353
#define ll long long
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f
inline int read()
{
	char ch=getchar(); int nega=1; while(!isdigit(ch)) {if(ch=='-') nega=-1; ch=getchar();}
	int ans=0; while(isdigit(ch)) {ans=ans*10+ch-48;ch=getchar();}
	if(nega==-1) return -ans;
	return ans;
}
void print(vector<int> x){for(int i=0;i<(int)x.size();i++) printf("%d%c",x[i]," \n"[i==(int)x.size()-1]);}
#define N 100005
char s[N];
int n;
signed main()
{
	scanf("%s",s+1); n=strlen(s+1);
	int als=1;
	for(int i=1;i<n;i++) als&=s[i]==s[i+1];
	if(als) printf("%c\n",s[1]);
	else
	{
		if(s[1]==s[n]) printf("%c%c%c\n",s[1],s[1]^1,s[1]);
		else printf("%c%c\n",s[1],s[n]);
	}
	return 0;
}