#include <stdio.h>
#include <math.h>
int main() 
{
    int max = 0;
    int n = 0;
    scanf("%d",&n);
    int num = 0;
    for(int i = 0;i<n;i++)
    {
        scanf("%d",&num);

        if((int)pow((int)sqrt(num),2) != num)
        {
            if(num>max)
            {
                max = num;
            }
        }
 
    }
    printf("%d\n",max);
    
    return 0;
}