Intervale_AB

#include <bits/stdc++.h>

using namespace std;

ifstream f("intervale.in");
ofstream g("intervale.out");

struct intervale{
    char c;
    int val;

    bool operator < (const intervale &y) const {
        return val < y.val;
    }

} v[200001];

int n, i, maxx, nr, sum, a, b;

int main() {

    f >> n;
    for(i = 1; i <= n; i++) {
        f >> a >> b;
        v[2 * i - 1].val = a, v[2 * i - 1].c = 'a';
        v[2 * i].val = b + 1, v[2 * i].c = 'b';
    }

    sort(v + 1, v + 2 * n + 1);

    i = 1;
    while(i <= 2 * n) {
        nr = v[i].val;
        while(v[i].val == nr && i <= 2 * n) {

            if(v[i].c == 'a') sum++;
            if(v[i].c == 'b') sum--;
            i++;
        }

        if(sum > maxx)
            maxx = sum;
    }

    g << maxx;
    return 0;
}