#include <cstdio>

using namespace std;

typedef long long int int_64b;

int_64b c (int_64b x) {
    for (int d = 2; ; d ++) if (x % d) return d;
    return 0;
}

int power (int_64b x) {
    return ((x == 2) ? 1 : ((power (c (x))) + 1));
}

int main () {
    int_64b a, b, out = 0;
    scanf ("%lld%lld", & a, & b);
    for (int_64b x = a; x <= b; x ++) out += (power (x));
    printf ("%lld\n", out);
    return 0;
}