#include <stdio.h>
#include <malloc.h>

#define max(x,y) ((x) >= (y)) ? (x) : (y)

int main() {
    int n;
    int *last = calloc(101, sizeof(int));
    FILE *input = fopen("input.txt", "r");
    fscanf(input, "%d", &n);
    int maxDifference = 0;
    for(int min = 1; min <= n; ++min) {
        int route;
        fscanf(input, "%d", &route);
        if(last[route] != 0) {
            int difference = min - last[route];
            maxDifference = max(maxDifference, difference);
        }
        last[route] = min;
    }
    free(last);
    fclose(input);
    FILE *output = fopen("output.txt", "w");
    fprintf(output, "%d", maxDifference);
    fclose(output);
    return 0;
}