546D - Soldier and Number Game - CodeForces Solution

#include <bits/stdc++.h>

using namespace std;

const int N = 5000000;

long long v[N + 5];

void solve() {
    for(int i = 2; i <= 5000000; ++i)
    {
        if(v[i] == 0)
        {
            for(int j = i; j <= 5000000; j += i)
            {
                int x = j;
                while(x % i == 0)
                    v[j]++, x /= i;
            }
        }
    }
    for(int i = 2; i <= 5000000; ++i)
        v[i] += v[i-1];
    int t;
    cin >> t;
    for (int i = 0; i < t; i++) {
        int a, b;
        cin >> a >> b;
        cout << v[a] - v[b] << '\n';
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
}