// editor2
#include<stdio.h>
#include<math.h>
#include<stdbool.h>
bool isPrime(int num)
{
    if (num < 2)
    return false;
    for (int i = 2; i <= sqrt(num); i++)
    {
        if (num % i ==0)
        return false;
    }
    return true;
}
void findlargestPrime(int *arr, int m,int n)
{
    int largest = -1;
    int *ptr = arr;
    for (int i = 0; i < m * n; i++)
    {
        if (isPrime(*(ptr + i)))
        {
            if (*(ptr + i) > largest)
            largest = *(ptr + i);
        }
    }
    if (largest != -1)
    printf("%d\n", largest);
    else
    printf("No prime number found.\n");
}
int main()
{
    int m,n;
    scanf("%d %d", &m, &n);
    int matrix[m][n];
    for (int i = 0; i < m; i++)
    {
        for(int j =0; j < n; j++)
        {
        scanf("%d", &matrix[i][j]);
        }
    }
    findLargestPrime(&matrix[0][0], m,n);
    return 0;
}