Doing python exercises already I've a problem with string:

```
#!/usr/bin/python

str = 'mandarino'
indice = len(str)-1
#print ("indice is:",indice)

while indice > 0:
        lett = str[indice]
        print (lett)
        indice = indice -1

```

Putting off "-1" the results is:

```
IndexError: string index out of range

```