Interleaving of numbers P72315

We define the interleaving of two natural numbers with d digits x=x_dx_d−1… x₂x₁ and y=y_dy_d−1… y₂y₁ as x_dy_dx_d−1y_d−1… x₂y₂x₁y₁. For example, the interleaving of 4123 and 5679 is 45162739. Write a program that reads pairs of natural numbers and prints their interleavings.

For the sake of practice, define and use a function

to compute the interleaving of two natural numbers x and y.

Input

Input consists of several pairs of natural numbers with the same number of digits.

Output

Print the interleaving of every given pair.

Observation

To avoid overflows, no given number will have more than four digits, but your program should not take this fact into account.