#include <bits/stdc++.h> #define fi first #define se second #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 FORLL(i, a, b) for (ll i = a, _b = b; i <= _b; ++i) #define FORDLL(i, a, b) for (ll i = a, _b = b; i >= _b; --i) #define all(x) x.begin(), x.end() #define uni(x) sort(all(x)), x.erase(unique(all(x)), x.end()) using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<int, int> pii; typedef pair<ll, ll> pll; #define dbg(...) debug(#__VA_ARGS__, __VA_ARGS__) template<typename T> void __prine_one(const char *&s, const T &x) { while (*s == ' ') ++s; const char *p = s; int bal = 0; while (*s) { if (*s == '(') ++bal; else if (*s == ')') --bal; else if (*s == ',' && bal == 0) break; ++s; } cerr.write(p, s - p) << " = " << x; if (*s == ',') { cerr << " , "; ++s; } } template<typename... Args> void debug(const char *s, Args... args) { cerr << "[ "; int dummy[] = {0, (__prine_one(s, args), 0)...}; (void)dummy; cerr << " ]\n\n"; } // -------------------------------------------------------------------------------------------- const int maxn = 1e5 + 3; int n, POS[maxn], q, m; struct Segment { int s, e; bool operator == (const Segment &other) const { return s == other.s && e == other.e; } bool operator < (const Segment &other) const { if (s == other.s) return e < other.e; return s < other.s; } } a[maxn]; vector<Segment> S; pii seg[maxn << 2], nx[maxn][20]; vector<int> ids; // -------------------------------------------------------------------------------------------- void upd(int id, int l, int r, int pos, pii val) { if (l == r) { seg[id] = min(seg[id], val); return; } int mid = l + r >> 1; if (pos <= mid) upd(id << 1, l, mid, pos, val); else upd(id << 1 | 1, mid + 1, r, pos, val); seg[id] = min(seg[id << 1], seg[id << 1 | 1]); } pii get(int id, int l, int r, int u, int v) { if (l > v || r < u) return {(int)1e9, (int)1e9}; if (l >= u && r <= v) return seg[id]; int mid = l + r >> 1; return min(get(id << 1, l, mid, u, v), get(id << 1 | 1, mid + 1, r, u, v)); } void process() { int u, v; cin >> u >> v; u = POS[u]; v = POS[v]; if (v < u) return void(cout << "impossible\n"); if (u == v) return void(cout << "0\n"); int res = 0; FORD(i, 19, 0) { int cur_nx = nx[v][i].se; if (cur_nx == 1e9 || S[cur_nx].s <= S[u].e) continue; res += 1 << i; v = cur_nx; } if (nx[v][0].se == 1e9 || S[nx[v][0].se].s > S[u].e) return void(cout << "impossible\n"); v = nx[v][0].se; ++res; res += u != v; cout << res << '\n'; } void solve() { cin >> n >> q; FOR(i, 1, n << 2) seg[i] = {(int)1e9, (int)1e9}; S.push_back({0, 0}); FOR(i, 1, n) { cin >> a[i].s >> a[i].e; S.push_back({a[i].s, a[i].e}); ids.push_back(a[i].s); ids.push_back(a[i].e); } uni(S); uni(ids); // for (const auto &e : S) // dbg(e.s, e.e); FOR(i, 1, n) { POS[i] = lower_bound(all(S), a[i]) - S.begin(); } m = (int)S.size() - 1; for (auto &e : S) { e.s = lower_bound(all(ids), e.s) - ids.begin() + 1; e.e = lower_bound(all(ids), e.e) - ids.begin() + 1; } FOR(i, 1, m) { pii cur = get(1, 1, (int)ids.size(), S[i].s, S[i].e); nx[i][0] = cur; // dbg(i, cur.fi, cur.se); upd(1, 1, (int)ids.size(), S[i].e, pii(S[i].s, i)); } FOR(j, 1, 19) FOR(i, 1, m) { nx[i][j] = nx[i][j - 1]; if (nx[i][j - 1].se != 1e9) nx[i][j] = min(nx[i][j - 1], nx[nx[i][j - 1].se][j - 1]); } while (q--) { process(); } } signed main() { ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); #define TASK "TEST" if (fopen(TASK".INP", "r")) { freopen(TASK".INP", "r", stdin); freopen(TASK".OUT", "w", stdout); } solve(); return 0; }

events.cpp: In function 'int main()':
events.cpp:190:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  190 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
events.cpp:191:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  191 |         freopen(TASK".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~