import java.util.Scanner;
public class Main{
public static void main
(String[] args
){ Scanner in
= new Scanner
(System.
in);
s = s.toUpperCase();
int[] count = new int[26];
for(int i = 0; i < s.length(); i++){
int a = s.charAt(i);
count[a-65]++;
}
int max = count[0];
int idx = 0;
for(int i = 1; i < 26; i++){
if(count[i] > max){
max = count[i];
idx = i;
}
}
int resultCount = 0;
for(int i = 1; i < 26; i++){
if(max == count[i])resultCount++;
}
if(resultCount > 1){
}else{
System.
out.
println((char)(idx
+ 65)); }
}
}
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