import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int count = 0;
int a = 0;
int b = 0;
a = n / 7;
b = n % 7 + 7;
if (b == 13) {
count = a + 2;
} else if (b == 12) {
count = a + 1;
} else if (b == 11) {
count = a -1 +3;
} else if(b == 10){
count = a - 1 + 2;
} else if (b == 9) {
count = a + 2;
} else if (b == 8) {
count = a + 1;
}
else count = a;
System.out.println(count);
sc.close();
}
}

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