/* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
{
//input string in input1
Scanner sc
=new Scanner
(System.
in); int count[]=new int[26];
int max=-1,sum=0,i;
for(i=0;i<26;i++){
count[i]=0;
}
char[] a=input1.toLowerCase().toCharArray();
for(i=0;i<a.length;i++){
count[a[i]-97]++;
}
for(i=0;i<26;i++){
if(count[i]!=0 && count[i]%2==0){
sum=sum+((count[i])/2);
}
else{
if(count[i]>max){
max=count[i];
}
}
}
if(max!=-1){
sum+=(max/2)+1;
}
System.
out.
println("Result is"+sum
);
}
//result is there in sum
}
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