#include <iostream>
using namespace std;
int A,B,k,ans;
bool ar[110000];
int main() {
for(int x=2; x<=100000; x++) ar[x] = true;
for(int x=2; x<=100000; x++) {
if(ar[x]) {
for(int y=x+x; y<=100000; y+=x) {
ar[y] = false;
}
}
}
cin >> A >> B;
for(int x = A; x<=B; x++) {
int cnt = 0;
k = x;
for(int y=2; y*y<=x && k >1; y++) {
while(k%y == 0 && k > 1) {
k/=y;
cnt++;
}
}
if(k>1) cnt++;
if(ar[cnt]) ans++;
}
cout<<ans;
}