D.cpp

#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define EACH(it,a) for(__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)

#define DEBUG(x) { cout << #x << " = "; cout << (x) << endl; }
#define PR(a,n) { cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl; }
#define PR0(a,n) { cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl; }

#define sqr(x) ((x) * (x))
using namespace std;

const int MN = 5000111;
int sieve[MN], f[MN];

void init() {
    FOR(i,2,3000) if (!sieve[i]) {
        for(int j=i*i; j < MN; j += i)
            sieve[j] = i;
    }
}

int main() {
    ios :: sync_with_stdio(false);
    init();
    FOR(i,1,MN-1) {
        if (i == 1) f[i] = 0;
        else {
            f[i] = f[i-1];
            int u = i;
            while (u > 1) {
                int p = sieve[u] ? sieve[u] : u;
                u /= p;
                f[i]++;
            }
        }
    }
    int t; scanf("%d", &t);
    while (t--) {
        int a, b; scanf("%d%d", &a, &b);
        printf("%d\n", f[a] - f[b]);
    }
    return 0;
}