#include <stdio.h>
#include <string.h>

int main(void) {
    char s[1001], t[1001];
    int i, j, l, x[1001][1001];
    while (scanf("%s", s) == 1) {
        t[j = l = strlen(s)] = 0;
        for (i = 0, j--; i < l; i++, j--)
            t[j] = s[i];
        for (i = 0; i <= l; i++)
            x[i][0] = x[0][i] = 0;
        for (i = 1; i <= l; i++)
            for (j = 1; j <= l; j++)
                x[i][j] =
                    (s[l - i] == t[l - j]) ? (1 + x[i - 1][j - 1]) :
                    (x[i][j - 1] > x[i - 1][j]) ? x[i][j - 1] :
                    x[i - 1][j];
        printf("%d\n", x[l][l]);
    }
    return 0;
}