import math

def is_perfect_square(num):
    root = int(math.sqrt(num))
    return root * root == num

def find_max_non_square(numbers):
    max_non_square = float('-inf')
    for num in numbers:
        if not is_perfect_square(num):
            max_non_square = max(max_non_square, num)
    return max_non_square

def main():
    n = int(input().strip())
    numbers = list(map(int, input().strip().split()))
    
    result = find_max_non_square(numbers)
    print(result)

if __name__ == "__main__":
    main()