#include<iostream>
#include<fstream>
using namespace std;
bool isPrimeNumber(int n) {
int i=2;
while (n>1 && n%i!=0) {
i++;
}
return i==n;
}
int main() {
ifstream input;
input.open("D:\\Learning file in c++\\NTO.INP",ios_base::in);
long long a,b;
input>>a>>b;
input.close();
ofstream output;
output.open("D:\\Learning file in c++\\NTO.OUT",ios_base::out);
int count=0;
for (int i=a;i<=b;i++) {
if (isPrimeNumber(i)) {
count++;
}
}
output<<count;
output.close();
}
