import math

def replacements(c):
    allRepl = []
    pot = (10)**c
    for i in range(0, pot):
        allRepl.append(str(i).zfill(c))
    return allRepl

def allNums(s, r):
    for i in r:
        strin = ""
        count = 0
        strin += s[count]
        for letter in i:
            count += 1
            strin += letter
            strin += s[count]
        if(math.sqrt(int(strin)) == int(math.sqrt(int(strin)))):
            return int(math.sqrt(int(strin)))
    
knownNums = input()
numsString = input().rstrip().split()

c = int(knownNums)-1
print(allNums(numsString, replacements(c)))