#include <bits/stdc++.h>
#define SIZE 4000005
#define B1 89939927
#define B2 89939929
#define M1 1000000007
#define M2 1000000009
using namespace std;
typedef long long int ll;
typedef pair <ll,ll> P;

char str[SIZE];
ll h1[SIZE],h2[SIZE],t1[SIZE],t2[SIZE];
ll hr1[SIZE],hr2[SIZE];
int n;
P get_LH(int s,int t){
	ll c1=h1[t]-(s==0?0:h1[s-1]*t1[t-s+1]%M1)+M1;
	ll c2=h2[t]-(s==0?0:h2[s-1]*t2[t-s+1]%M2)+M2;
	c1%=M1,c2%=M2;
	return P(c1,c2);
}
P get_RH(int s,int t){
	ll c1=hr1[s]-(t==n-1?0:hr1[t+1]*t1[t-s+1]%M1)+M1;
	ll c2=hr2[s]-(t==n-1?0:hr2[t+1]*t2[t-s+1]%M2)+M2;
	c1%=M1,c2%=M2;
	return P(c1,c2);
}
bool foldable(int l,int r){
	return l%2==(r+1)%2&&get_LH(l,(l+r)/2)==get_RH((l+r+1)/2,r);
}
int main(){
	scanf("%s",&str);
	n=strlen(str);
	ll c1=0,c2=0;
	for(int i=0;i<n;i++){
		int c=str[i]-'A'+1;
		c1=(c1*B1+c)%M1;
		c2=(c2*B2+c)%M2;
		h1[i]=c1,h2[i]=c2;
	}
	t1[0]=t2[0]=1;
	for(int i=1;i<=n;i++){
		t1[i]=t1[i-1]*B1%M1;
		t2[i]=t2[i-1]*B2%M2;
	}
	c1=0,c2=0;
	for(int i=n-1;i>=0;i--){
		int c=str[i]-'A'+1;
		c1=(c1*B1+c)%M1;
		c2=(c2*B2+c)%M2;
		hr1[i]=c1,hr2[i]=c2;
	}
	//printf("%lld %lld\n",get_LH(0,1).first,get_LH(0,1).second);
	//printf("%lld %lld\n",get_RH(2,3).first,get_RH(2,3).second);
	int l=0,r=n-1;
	while(1){
		bool up=false;
		for(int k=1;k*2<=r-l+1;k++){
			if(foldable(l,l+2*k-1)){
				l+=k;
				up=true;
				break;
			}
			if(foldable(r-2*k+1,r)){
				r-=k;
				up=true;
				break;
			}
		}
		if(!up) break;
	}
	printf("%d\n",r-l+1);
}