Gandalf’s search for the history of the One Ring took him to the library of Minas Babel, under the care of Archivist Borges. This library contains every possible book - true and false, nonsensical and insightful - and Gandalf must use all of this wisdom to find the true account of the Ring.</p>

Given that there are C possible characters, W characters in a line, L lines on a page, and P pages in a book, tell how many books are in the library of Minas Babel, if each possible book appears exactly once.

For example, if the library were to contain books with 2 characters (a,b), 3 characters per line, one line per page, and one page per book, then the following books would be in the library: aaa aab aba abb baa bab bba bbb

입력 형식

Each test case is on its own line, each of the form C W L P; all are non-negative integers. The end of input is marked by a line of the form ”0 0 0 0”, which should produce no output.

출력 형식

For each test case, output a new line containing a single integer, which should represent the number of books in the library.

예제 입력

4 2 2 2
4 3 2 2
0 0 0 0

예제 출력

65536
16777216