九度 1465：最简真分数

#include <iostream>
#include <stdio.h>
#include <algorithm>
using namespace std;

int numbers[700];

int gcd(int x, int y) {
    if(x == 1 || y == 1)
        return 1;
    if(x == y)
        return x;

    if(x < y)
        swap(x, y);

    if(x&1 == 1) {
        if(y&1 == 1)
            return gcd(x-y, y);
        else
            return gcd(x, y/2); 
    }else {
        if(y&1 == 1)
            return gcd(x/2, y);
        else
            return 2*gcd(x/2, y/2);
    }
}

int main() {
    int n;
    while(scanf("%d", &n) != EOF && n != 0) {
        for(int i = 0; i < n; i ++)
            scanf("%d", numbers+i);

        sort(numbers, numbers + n);

        int cnt = 0;
        for(int i = 0; i < n; i ++) {
            for(int j = i+1; j < n; j ++)
                if(gcd(numbers[i], numbers[j]) == 1)
                    cnt ++;
        }
        cout << cnt << endl;
    }
    return 0;
}