4641번: Doubles

#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
    int num[100], in = 1, count, max, ans;
    while (1)
    {
        ans = 0;
        count = 0;
        max = 0;
        do
        {
            scanf("%d", &in);
            if (in == -1)
                return 1;
            num[count++] = in;
        } while (in != 0);
        sort(num, num + count - 1);
        max = num[count - 2];
        max /= 2;
        for (int i = 0; num[i] <= max; ++i)
            for (int j = i + 1; j < count - 1; ++j)
            {
                if (num[i] * 2 == num[j])
                {
                    ++ans;
                    break;
                }
                else if (num[i] * 2 < num[j])
                    break;
            }
        printf("%d\n", ans);
    }
}