def main():
	 n = int(input())
	 s = list(input())
	 s = [ord(i) for i in s]

	 for i in range(n-1):
	 	if s[i] > s[i+1]:
	 		print("YES")
	 		print(i+1, i+2)
	 		return
	 print("NO")

if __name__ == "__main__":
	main()

