// This method can calculate nCr upto n = 66. The largest value for nCr
// that can be stored in a Java long variable is 7,219,428,434,016,265,740
// (for n = 66, r = 33). The range of the type long in Java is from
// -2^63 to 2^63-1. This method uses an array to store the prime factors
//...