#!/usr/bin/env python3

# Brute force
from math import sqrt

def main():
    low = 10*(int(sqrt(10203040506070809))//10)
    upp = int(sqrt(19293949596979899))
    for i in range(low+3, upp+1, 10):
        if is_num(i**2):
            return i*10
    for i in range(low+7, upp+1, 10):
        if is_num(i**2):
            return i*10
    return False

def is_num(n):
    s = str(n)
    for i in range(9):
        if int(s[2*i]) != i+1: return False
    return True

print(main())