Interleaving of numbers P72315

We define the interleaving of two natural numbers with $d$ digits $x=x_dx_{d-1}\dots x_2x_1$ and $y=y_dy_{d-1}\dots y_2y_1$ as $x_{d}y_dx_{d-1}y_{d-1}\dots x_2y_2x_1y_1$. 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

    int interleaving(int x, int y);

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.