# Define a procedure, find_last, that takes as input
# two strings, a search string and a target string,
# and returns the last position in the search string
# where the target string appears, or -1 if there
# are no occurrences.
#
# Example: find_last('aaaa', 'a') returns 3

# Make sure your procedure has a return statement.

def find_last(x,y):
    
    
    pos= x.find(y)
    if pos==-1:
        return -1
    else:
        
        while True:
                    
            next_pos=x.find(y,pos+1)
            pos=pos+1

            if next_pos==-1:
                return pos-1
        
   
        
print (find_last("aaaa", "a"))
#>>> 3

print (find_last('aaaaa', 'aa'))
#>>> 3

#print (find_last('aaaa', 'b'))
#>>> -1

#print (find_last("111111111", "1"))
#>>> 8

#print (find_last("222222222", ""))
#>>> 9

#print (find_last("", "3"))
#>>> -1

#print (find_last("", ""))
#>>> 0
