#include <iostream>
using namespace std;

long long count_magic(long long X) {
    if (X < 7) return 0;
    
    long long divisible_by_7 = X / 7;  
    long long ends_with_7 = (X - 7) / 10 + 1;
    long long both = (X - 7) / 70 + 1;  
    
    return divisible_by_7 + ends_with_7 - both;
}

int main() {
    long long k;
    cin >> k;

    long long left = 1, right = 2e18; 
    long long answer = 0;
    
    while (left <= right) {
        long long mid = left + (right - left) / 2;
        
        if (count_magic(mid) >= k) {
            answer = mid;
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    
    cout << answer;
    
    return 0;
}