#include <bits/stdc++.h>

using namespace std;

constexpr int maxn = 4000005;

int go[maxn][5], par[maxn], val[maxn], last, pam_cnt;
int dp[maxn], id[maxn];

char s[maxn];

void extend(int n) {
	int p = last, c = s[n];
	while (s[n - val[p] - 1] != s[n])
		p = par[p];
	
	if (!go[p][c]) {
		int q = ++pam_cnt, now = p;
		val[q] = val[p] + 2;
		do
			p = par[p];
		while (s[n - val[p] - 1] != s[n]);

		par[q] = go[p][c];
		last = go[now][c] = q;

		// dp[q] = (val[q] % 2 == 0 ? q : dp[par[q]]);
	}
	else
		last = go[p][c];
}

void work(int n, bool *f) {
	par[0] = pam_cnt = 1;
	val[1] = -1;

	for (int i = 1; i <= n; i++) {
		extend(i);
		id[i] = last;
	}

	memset(dp, -1, sizeof(dp));

	for (int i = 1; i <= pam_cnt; i++) {
		dp[i] = dp[par[i]];

		if (val[i] % 2 == 0) {
			if (dp[i] == -1)
				dp[i] = val[i];
		}

		// printf("dp[%d] = %d\n", i, dp[i]);
	}
	
	int i = n;
	f[n] = true;
	while (dp[id[i]] != -1) {
		assert(dp[id[i]] % 2 == 0);

		// printf("i = %d  -= %d\n", i, dp[id[i]] / 2);

		i -= dp[id[i]] / 2;
		f[i] = true;
	}

	for (int i = 0; i <= pam_cnt; i++) {
		memset(go[i], 0, sizeof(go[i]));
		par[i] = val[i] = dp[i] = 0;
	}

	last = pam_cnt = 0;

	for (int i = 0; i <= n; i++)
		id[i] = 0;
}

bool f[maxn], g[maxn];

char t[maxn];

int main() {

	scanf("%s", t + 1);
	int n = strlen(t + 1);

	for (int i = 1; i <= n; i++) {
		if (t[i] == 'A')
			s[i] = 1;
		else if (t[i] == 'C')
			s[i] = 2;
		else if (t[i] == 'G')
			s[i] = 3;
		else if (t[i] == 'T')
			s[i] = 4;
		else
			assert(false);
	}

	work(n, f);
	
	reverse(s + 1, s + n + 1);
	work(n, g);
	reverse(g + 1, g + n + 1);

	int ans = n + 114514;

	int last = -1;
	for (int i = 1; i <= n; i++) {
		if (g[i])
			last = i;
		
		if (f[i] && last > 0)
			ans = min(ans, i - last + 1);
	}

	// printf("f:");
	// for (int i = 1; i <= n; i++)
	// 	printf(" %d", (int)f[i]);
	// printf("\n");

	// printf("g:");
	// for (int i = 1; i <= n; i++)
	// 	printf(" %d", (int)g[i]);
	// printf("\n");

	printf("%d\n", ans);

	return 0;
}