3.
#include <iostream>
using namespace std;
int main()
{
int a, b, p = 1;
cin >> a >> b;
for (int i = a; i <= b; i++)
{
p *= i;
}
cout << p;
return 0;
}
4.
#include <iostream>
using namespace std;
int main()
{
int a, b, num = 0;
cin >> a >> b;
for (int i = a; i < b; i++)
{
if (i % 7 == 0)
{
num++;
}
}
cout << num;
return 0;
}