#include<iostream>
#include<cstring>
using namespace std;
int main()
{char s[256],voc[]="aeiou";
 int i,n,v[5]={0},c;
 cin.get(s,256);n=strlen(s);
 for(i=0;i<=n;i++)
 { if(s[i]>='a'&&s[i]<='z')
     c=s[i];
  else if (s[i]>='A'&&s[i]<='Z')
      c=s[i]+32;
      if(strchr(voc,c)!=0)
      v[strchr(voc,c)-voc]++;
 }
 int maxx=0;
 for(i=0;i<5;i++)
     if(v[i]>maxx){maxx=v[i];c=voc[i]-32;}
 cout<<c;
 return 0;
}