JAVA高精计算

      为了偷懒，专门用了JAVA高精。果然很简单。但是在使用前一定要注意审题，有时候根本不需要用高精计算。一定要有看清条件。   
BigInteger
                       初始化 从string到BigInteger:
                                   //从int到string            tring a=String.valueof(int b);
                                   BigInteger big=new BigInteger(string a);
                       从BigInteger到int
                                    int b=big.intValue()
                       从int到BigInteger:
                                   big=BigInteger.valeOf(int b);
                       从BigInteger到string:
                          &n