C++ solution for problem C (with binary search)

#include <cstring>
#include <map>
#include <deque>
#include <queue>
#include <stack>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <algorithm>
#include <vector>
#include <set>
#include <complex>
#include <list>
#include <climits>
#include <cctype>

using namespace std;

vector<pair<int, int> > factors;
void getFactors(int n) {
    factors.clear();
    int d = 1;
    for (int i = 2; i * i <= n; i += d, d = 2)
        if (n % i == 0) {
            factors.push_back(make_pair(i, 0));
            while (n % i == 0) {
                n /= i;
                factors.back().second++;
            }
        }
    if (n != 1)
        factors.push_back(make_pair(n, 1));
}

vector<int> divisors;
void getDivisors(int ind = 0, int res = 1) {
    if (ind == (int) factors.size()) {
        divisors.push_back(res);
        return;
    }
    for (int i = 0; i <= factors[ind].second; i++) {
        getDivisors(ind + 1, res);
        res *= factors[ind].first;
    }
}

int main() {
    int a, b, n;
    scanf("%d", &a);
    getFactors(a);
    getDivisors();
    vector<int> d1 = divisors;
    scanf("%d", &b);
    getFactors(b);
    divisors.clear();
    getDivisors();
    vector<int> d2 = divisors;
    sort(d1.begin(), d1.end());
    sort(d2.begin(), d2.end());
    vector<int> cd;
    set_intersection(d1.begin(), d1.end(), d2.begin(), d2.end(), inserter(cd,
            cd.begin()));
    scanf("%d", &n);
    int low, high, ind;
    for (int i = 0; i < n; i++) {
        scanf("%d%d", &low, &high);
        ind = upper_bound(cd.begin(), cd.end(), high) - cd.begin();
        ind--;
        if (ind == -1 || cd[ind] < low)
            printf("-1\n");
        else
            printf("%d\n", cd[ind]);
    }
    return 0;
}