第k个幸运数
//大神看看，这样可以不
#include <string>
using namespace std;
int main()
{
int num = 16;
while (cin>>num)
{
num--;
string str;
int n = log(num / 2 + 1)/log(2);
int m=num-(1<<(n+1))+2;
for (int i = 0; i <= n; i++)
{
str += (m & 1) ? "7" : "4";
m >>= 1;
}
reverse(str.begin(), str.end());
cout << str << endl;
}
return 0;
}
