n = gets.chomp.to_i
numbers = []
while (line = gets)
	max = line.chomp.split('').max
	if max >= '0' && max <= '9'
		base = max.to_i + 1
	else
		base = max.ord - 'A'.ord + 10 + 1
	end
	numbers << line.chomp.to_i(base)
end
puts numbers.min