#include<fstream.h>
ifstream f("ordine.in");
ofstream g("ordine.out");
int main()
{long a[26]={0},n=0,i,x,y;
char c,z;
f>>c;
while(!f.eof())
{a[c-97]++;n++;
f>>c;
}

c='.';
while(n)
{y=1;
for(i=0;i<26;i++)
{if(a[i]!=0&&char(97+i)!=c&&y){x=i;z=char(97+i);y=0;}
if(a[i]>=(n/2+1)){x=i;z=char(97+i);break;}}
if(z!=c)
{
	g<<z;
	n--;
	c=z;
	a[x]--;
}
}


f.close();
g.close();
return 1;
}