NYoj 28 大数阶乘

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用JAVA的大数类写的，代码如下：

import java.math.*;
import java.io.*;
import java.io.InputStreamReader;
import java.io.IOException;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String str = in.readLine();
        int n = Integer.parseInt(str);
        BigInteger ans = new BigInteger(String.valueOf(1));
        for(int i=2; i<=n; ++i) {
            ans = ans.multiply(new BigInteger(String.valueOf(i)));
        }
        System.out.println(ans);
    }
}