#include <fstream>

using namespace std;

ifstream f("mins.in");
ofstream g("mins.out");

int v[200005],n,d,c;

void solve();
int Max(int,int);

int main()
{
    f>>d>>c;
    c--,d--;
    solve();
    return 0;
}

void solve()
{
    int min=-Max(-c,-d),max=Max(c,d);
    int i=2;
    while (i*i<=max)
    {
        int j=2;
        if (!v[i])
        while (j*i<=max)
        {
            v[j*i]=max;
            j++;
        }
        i++;
    }
    int p=0,p1=0;
    for (int i=1;i<=max;i++)
    {
        if (i<=d && !v[i]) p++;
        if (i<=c && !v[i]) p1++;
    }
    g<<p*p1-min+1;
}

int Max(int a,int b)
{
    if (a>b) return a;
    return b;
}