#include
using namespace std;
#include
int main()
{
vector v1{-1,3,4,6,10,13,14,15,17,21}; //容器v1
int target;
cin >> target;
int low = 0, high = v1.size() - 1, mid;
while (low <= high)
{
mid = (low + high) / 2;
if (v1[mid] == target)
{
cout << mid << endl;
return mid;
}
else if (v1[mid] < target)
low = mid + 1;
else if (v1[mid] > target)
high = mid - 1;
}
system("pause");
return -1;
}