include

using namespace std;

int main() {

int a, b, c;
int sum = 0;
cin >> a >> b >> c;
for (int i = a; i <= b; i++) {
	if (c == 6 || c == 7) {
		sum++;
	}
	if (c == 7) {
		c = 1;
	} else {
		c++;
	}
}
cout << sum;
return 0;

}