fibonacci series
#fibonacci series is special type of sequence
#fibonacci series is somethinng liket this-->
#0,1,1,2,3,5,8,13,21,34,55,89.......
#addition of former two succesive number results in the third element.
#in simple way as given in above series that 0,1,1--> where 0+1=1 e,i; 1
#example: 2,3,5 addition of 2 and 3 results in latter element in sequence e,i 5
8,13,21 : 8 + 13=21
34,55,89: 34 + 55=89