import std;
import core.bitop;
import core.checkedint;
import core.time;

void main() {
	const x = readln.chomp.to!int;
	int a = 0, b = 0, c = 0;
	while(a != x) {
		if(c <= 1 || c == 4) {
			a += 2;
			b += 2;
		} else {
			a--;
			b++;
		}
		c++;
		c %= 7;
		// writeln(a);
	}
	writeln(b);
}