Full question:
Given N step stair, how many number of ways can you climb if you use either 1 or 2 at a time?
Answer
It will be F(n+1) fibonacci number, there Fibonacci numbers are defined by the recurrence relation:
F(n) = F(n-2) + F(n-1)
for N stair number of ways will be
N=1 => 1 = F(2)
N=2 => 2 = F(3)
N=3 => 3 = F(4)
N=4 => 5 = F(5)
N=5 => 8 = F(6)
N=6 => 13 = F(7)
....
Fibonacci numbers on Wikipedia
Given N step stair, how many number of ways can you climb if you use either 1 or 2 at a time?
Answer
It will be F(n+1) fibonacci number, there Fibonacci numbers are defined by the recurrence relation:
F(n) = F(n-2) + F(n-1)
for N stair number of ways will be
N=1 => 1 = F(2)
N=2 => 2 = F(3)
N=3 => 3 = F(4)
N=4 => 5 = F(5)
N=5 => 8 = F(6)
N=6 => 13 = F(7)
....
N=k => F(k+1)
Fibonacci numbers on Wikipedia