package com.xiaojihua.datastructure;public class Zhishu {	public static void main(String[] args) {		// TODO Auto-generated method stub		System.out.println(probRelPrim(20));	}	/**	 * 欧几里得算法，求两个整数的最大公因数	 * @param m	 * @param n	 * @return	 */	public static long gcd(long m,long n){		while(n != 0){			long rem = m%n;			m = n;			n = rem;		}		return m;	}	public static double probRelPrim(int n){		int rel = 0, tot = 0;		for(int i=1; i<=n; i++){			for(int j=i+1; j<=n; j++){				tot++;				if(gcd(i,j)==1){					rel++;				}			}		}		return (double)rel/tot;	}}