Tetration, represented as a^^b, is repeated exponentiation. For example, 2^^3 is 2^2^2, which is 16.

Given two numbers a and b, print a^^b.

Test cases

1 2 -> 1 2 2 -> 4 5 2 -> 3125 3 3 -> 7625597484987 etc. 

^{Scientific notation is acceptable.}

Remember, this is code-golf, so the code with the smallest number of bytes wins.