Update climbing-stairs.py

Author: kamyu104

Python/climbing-stairs.py

@@ -27,7 +27,7 @@ def matrix_mult(A, B):
 
         T = [[1, 1],
              [1, 0]]
-        return matrix_mult([[1,  1]], matrix_expo(T, n-1))[0][0]  # [a1, a0] * T^(n-1)
+        return matrix_mult([[1,  0]], matrix_expo(T, n))[0][0]  # [a0, a(-1)] * T^n
 
 
 # Time:  O(n)