<snippet>
    <content><![CDATA[
template<typename T>
void seg_insert(std::set<std::pair<T, T>> &s, T l, T r) {
    while (true) {
        auto it = s.upper_bound({l, -1});
        if (it == s.end() || it->first > r + 1) {
            break;
        }
        r = std::max(r, it->second);
        s.erase(it);
    }
    while (true) {
        auto it = s.upper_bound({l, -1});
        if (it == s.begin() || (--it)->second < l - 1) {
            break;
        }
        l = std::min(l, it->first);
        r = std::max(r, it->second);
        s.erase(it);
    }
    s.insert({l, r});
}
]]></content>
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</snippet>