#include <stdio.h>
int main()
{
    int a,b,c=0;
    scanf("%d %d",&a,&b);
    if (a<0 || b<0 || a>b)
    {
        printf("Invalid input");
        return 0;
    }
    for (int i=a;i<=b;i++)
    if(i%7==0)
    c+=1;
    prinf("%d",c);
    return 0;
}