int position(int a[2015])
{
    int k = 2015;
    int low, high, mid;
    low = 0;
    high = 2015 - 1;
    while (low <= high) {
        mid = (low + high) / 2;
        if (k > a[mid]) {
            low = mid + 1;
        }
        if (k < a[mid]) {
            high = mid - 1;
        }
        if (k == a[mid]) {
            //从第1位开始算的位置
            return (mid + 1);
            //从第0位开始算的位置
            //return mid;
        }
    }
    return -1;
}