C :

#include<stdio.h>
char a[200];
int pan(int a,int b);
int main()
{
	scanf("%s",a);
	int x=0;
	for(;a[x]!='\0';x++);
	int ans=x;
	while(pan(0,x-1))
	{
		ans/=2;
		x/=2;
	}
	printf("%d",ans);
	return 0;
}
int pan(int m,int n)
{
    int mid=(m+n)/2;
    for(int i=m;i<=mid;i++)
    if(a[i]!=a[n-i]) return 0;
    return 1;
}

C++ :

#include <iostream>
#include <cstring>
using namespace std;

//判断是否回文
bool huiwen(char s[]){
	bool f = true;
	int i;
	for (i = 0;i < strlen(s) / 2;i++){
		if (s[i] != s[strlen(s) - i - 1]){
			f = false;
			break;
		}
	}
	return f;
} 

int main(){
	char s[2000];
	gets(s);
	int i;
	while (huiwen(s) && strlen(s) % 2 == 0){
		s[strlen(s) / 2] = '\0';
	}
    cout<<strlen(s)<<endl;
}

Pascal :

var str:string;
    b,i,x,c:longint;
begin
read(str);
b:=length(str);
while b mod 2=0 do
begin
c:=b;
for i:=1 to b do
if str[i]<>str[c-i+1] then  begin x:=1;break;end;
if x=1 then break
       else b:=b div 2;
end;
write(b);
end.

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.nextLine();
		while(str.substring(0, str.length()/2).equals(str.substring(str.length()/2,str.length())) ){
			str = str.substring(0, str.length()/2);
		}
		String str1 = str.substring(0, str.length()/2);
		System.out.println(str1.length());
	}
}

Python :

def huiwen(b):
    if b==b[::-1]:
        return 1
    else:
        return 0
str1=input()
while(huiwen(str1)):
    b=len(str1)
    str1=str1[0:int(b//2)]
print(len(str1))