UVa 11417

　　题目大意：关于最大公约数(Greatest Common Divisor, GCD)的，直接照着题目说的做就可以了。

#include <cstdio>

int gcd(int a, int b)
{
    return b == 0 ? a : gcd(b, a%b);
}

int main()
{
    int n;
    while (scanf("%d", &n) && n)
    {
        int g = 0;
        for (int i = 1; i < n; i++)
            for (int j = i+1; j <= n; j++)
                g += gcd(j, i);
        printf("%d
", g);
    }
    return 0;
}