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;
}