M=[0]
f=->k{
	M[k]||=k*B**(k-1)*(B-1)+f[k-1]
}

B = gets.to_i
D = (S=gets).to_i(B)
n = (1..S.size).bsearch{|k|
	D <= f[k]
}
DD = D+(B**n-1)/(B-1)-1
puts (DD/n).to_s(B)[DD%n]