题解 | #挑7#

#include <iostream>

using namespace std;

int main()
{
	int n = 0;
	int ans = 0;

	cin >> n;
	for (int i = 1; i <= n; ++i)
	{
		if (i % 7 == 0)
		{
			ans++;
		}
		else
		{
			int j = i;
			while (j != 0)
			{
				if ((j % 10) == 7)
				{
					ans++;
					break;
				}
				else
				{
					j = j / 10;
				}
			}
		}
	}

	cout << ans << endl;

	return 0;
}