#include<stdio.h>
char a[1003];
char ans[2][1003];
int l[2];
int main()
{
	scanf("%s", a);
	int i, j, k;
	int n, v;
	for (n = 0; a[n] != '\0'; n++);
	k = n - 1;
	for (i = n - 1; n - 1 - i <= i; i--)
	{
		v = 0;
		for (j = 1; j + i < n; j++)
			if (a[i + j] != a[i - j])
				v++;
		if (v == 0)
			k = i;
	}
	for (i = 0, l[0] = 0; i <= k; i++, l[0]++)
		ans[0][l[0]] = a[i];
	for (i = k - 1; i >= 0; i--, l[0]++)
		ans[0][l[0]] = a[i];
	ans[0][l[0]] = '\0';
	k = n - 1;
	for (i = n - 1; n - i - 1 <= i + 1; i--)
	{
		v = 0;
		for (j = 1; j + i < n; j++)
			if (a[i + j] != a[i - j + 1])
				v++;
		if (v == 0)
			k = i;
	}
	for (i = 0, l[1] = 0; i <= k; i++, l[1]++)
		ans[1][l[1]] = a[i];
	for (i = k; i >= 0; i--, l[1]++)
		ans[1][l[1]] = a[i];
	ans[1][l[1]] = '\0';
	if (l[0] < l[1])
		printf("%s\n", ans[0]);
	else
		printf("%s\n", ans[1]);
	return 0;
}