#include <bits/stdc++.h>

using namespace std;

#define REP(i, a, b) for (int i = (a), i##_end_ = (b); i < i##_end_; ++i)
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define mp make_pair
#define x first
#define y second
#define pb emplace_back
#define SZ(x) (int((x).size()))
#define ALL(x) (x).begin(), (x).end()

template<typename T> inline bool chkmin(T &a, const T &b) { return b < a ? a = b, 1 : 0; }
template<typename T> inline bool chkmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

typedef long long LL;

const int oo = 0x3f3f3f3f;

const int maxn = 4001000;

int expand[maxn + 5];

void manacher(char *s)
{
	static int f[(maxn << 1) + 5];
	static char ch[(maxn << 1) + 5];
	int n = strlen(s), id = 0, mx = 0;
	ch[0] = '$'; ch[1] = '#';
	for (int i = 1; i <= n; ++i)
		ch[i * 2] = s[i - 1], ch[i * 2 + 1] = '#';
	ch[n * 2 + 2] = '#';
	for (int i = 0; i <= 2 * n + 10; ++i) f[i] = 0;
	for (int i = 1; i <= 2 * n + 2; ++i)
	{
		if (i > mx) f[i] = 1;
		else f[i] = min(f[id * 2 - i], mx - i);
		while (ch[i - f[i]] == ch[i + f[i]]) ++f[i];
		if (i + f[i] > mx)
		{
			mx = i + f[i];
			id = i;
		}
	}
	REP(i, 0, n + 1) expand[i] = f[i * 2 + 1] >> 1;
	// expand[i]: expand from the gap before s[i] (0 indexed)
}

int n;
char s[maxn + 5];

bool visl[maxn + 5];
bool visr[maxn + 5];

vector<int> adjr[maxn + 5], adjl[maxn + 5];

int main()
{
#ifdef LOCAL
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
	scanf("%s", s);
	n = strlen(s);
	manacher(s);
	{
		int Min = n;
		visr[n] = 1;
		for (int i = n - 1; i >= 0; --i)
		{
			if (i + expand[i] >= Min)
			{
				visr[i] = 1;
				Min = i;
			}
		}
	}
	{
		int Max = 0;
		visl[0] = 1;
		REP(i, 1, n + 1)
		{
			if (i - expand[i] <= Max)
			{
				visl[i] = 1;
				Max = i;
			}
		}
	}
	int lstr = n;
	int ans = n;
	for (int i = n - 1; i >= 0; --i)
	{
		if (visl[i]) chkmin(ans, lstr - i);
		if (visr[i]) lstr = i;
	}
	printf("%d\n", ans);
	return 0;
}