Four positive integers $a, b, c, d$ are given. Find the square of any number if there exists a square with side lengths $a, b, c, d$. Print "\textbf{No}" otherwise. \InputFile Four positive integers $a, b, c, d$, each no more than $10^9$. \OutputFile If the square exists, print the square of any number. Otherwise print "\textbf{No}".