'hello world'[::-1]
'dlrow olleh'
In this particular example, the slice statement [::-1] means
start at the end of the string and end at position 0,
move with the step -1, negative one, which means one
step backwards.
#From w3schools.com
str1="Hello"
#if u want to take length input from user then use the next line
#n=int(input("enter the no of elements: ")) #this one
#if u don't wanna ask user the length then directly use this next line
n=len(str1)
for i in range(-1,-(n+1),-1):
print(str1[i],end='')
#prints olleh