f=->k{
	r=0
	0.upto(k){|i|
		r+=i*B**(i-1)*(B-1)
	}
	r
}

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]