#include <iostream>
#include "math.h"
using namespace std;
int main() {
    // insert code here...
    float n;
    float threeNum,fiveNum;
//    float fifteenNum;
    cin >> n;
    
//    fifteenNum = floor(n/15);
    threeNum = floor(n/3);
    fiveNum = floor(n/5);
    
    float ans = 2 * (threeNum + fiveNum);
    cout.precision(18);
    cout << ans <<endl;
    

    return 0;
}