1. Another Series

Problem to find the Nth number of the series, which is the sum of the previous four numbers.
There are predefined numbers as:
N1=1, N2=2, N3=3 and N4=4
You have to find the Nth number of the series.
Ni = N(i-1) + N(i-2) + N(i-3) + N(i-4) ; (i>=5)