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

int solution(int* colors, int n) {
    // Find rightmost house with different color from first house
    int maxDist1 = 0;
    for (int i = n - 1; i >= 0; i--) {
        if (colors[i] != colors[0]) {
            maxDist1 = i;
            break;
        }
    }
    
    // Find leftmost house with different color from last house
    int maxDist2 = 0;
    for (int i = 0; i < n; i++) {
        if (colors[i] != colors[n - 1]) {
            maxDist2 = (n - 1) - i;
            break;
        }
    }
    
    return maxDist1 > maxDist2 ? maxDist1 : maxDist2;
}

int main() {
    char line[10000];
    fgets(line, sizeof(line), stdin);
    
    int colors[1000];
    int n = 0;
    
    char* token = strtok(line + 1, ",]");
    while (token != NULL) {
        colors[n++] = atoi(token);
        token = strtok(NULL, ",]");
    }
    
    printf("%d\n", solution(colors, n));
    return 0;
}