#include <stdio.h>
#include <stdlib.h>
#pragma warning (disable: 4996)
int main (void)
{
    FILE *f;
    int n, m;
    int i;
    int *arr;
    int min=0;
    f=freopen("kek.txt", "r", stdin);
    if (f==NULL)
    {
        printf("Typidor.h\n");
        return -1;
    }
    scanf("%i%i", &n, &m);
    arr = (int*) malloc (m*n*sizeof(int *));
    for (i=0; i<n*m; i++)
    {
        scanf("%i", &arr[i]);
    }
    i=0;
    while (i!=n*m)
    {
        for (i=0; i<n*m; i++)
        {
            if (min == arr[i])
            {
                min++;
                break;
            }
        }
    }
    printf("%i", min);
    free(arr);
    fclose(f);
    return 0;
}