func main()
	const mod: int :: 1000000007
	var a: int :: cui@inputInt()
	var b: []char :: cui@input()
	
	var n: int :: ^b - 1
	var ans: int :: 0
	for i(1, n)
		if(i <> n)
			do ans :+ mod - math@modPow(a, i, mod)
			do ans :% mod
		else
			do ans :+ (n - 1) * math@modPow(a, i, mod)
			do ans :% mod
		end if
	end for
	
	do ans :+ mod - n * (math@modPow(a, n, mod) - 1) % mod
	do ans :% mod
	
	var t: int :: 0
	for i(0, n)
		do t :* a
		do t :+ b[i] $ int - '0' $ int
		do t :% mod
	end for
	do ans :+ t * n % mod
	do ans :% mod
	do cui@print("\{ans}\n")
end func