This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define fi first
#define se second
#define vi vector<int>
#define vll vector<long long>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng64(chrono::steady_clock::now().time_since_epoch().count());
inline int rand(int l,int r){return uniform_int_distribution<int>(l, r)(rng);}
inline ll rand(ll l,ll r){return uniform_int_distribution<ll>(l, r)(rng64);}
#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif
struct custom_hash {
static uint64_t splitmix64(uint64_t x) {
x += 0x9e3779b97f4a7c15;
x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
return x ^ (x >> 31);
}
size_t operator()(uint64_t x) const {
static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
return splitmix64(x + FIXED_RANDOM);
}
};
const int MAXN = 1e5 + 7;
const int BASE = (1 << 17);
const int MAXK = 20;
int pos[MAXN];
pii tree[2 * BASE + 7];
int range[MAXK][MAXN];
vector<pair<pii, int>> vec;
int n, q;
pii smaller(pii x, pii y){
if(x.fi != y.fi){
return (x.fi < y.fi ? x : y);
}
return (x.se < y.se ? x : y);
}
void upd(int ind, pii val){
ind += BASE;
tree[ind] = val;
ind /= 2;
while(ind > 0){
tree[ind] = smaller(tree[2 * ind], tree[2 * ind + 1]);
ind /= 2;
}
}
pii query(int v, int l, int p, int a, int b){
if(p < a || b < l){
return {1e9, 1e9};
}
if(a <= l && p <= b){
return tree[v];
}
int mid = (l + p) / 2;
return smaller(query(2 * v, l, mid, a, b), query(2 * v + 1, mid + 1, p, a, b));
}
void preprocessing(){
for(int i = 0; i < 2 * BASE + 7; i++){
tree[i] = {1e9, 1e9};
}
for(int i = 0; i < n; i++){
upd(i, {vec[i].fi.fi , i});
}
// cout << "RANGES\n";
for(int i = 0; i < n; i++){
int l = 0;
int p = i;
int s;
while(l < p){
s = (l + p) / 2;
if(vec[s].fi.se < vec[i].fi.fi){
l = s + 1;
}else{
p = s;
}
}
// cout << i << ' ' << l << ' ';
range[0][i] = query(1, 0, BASE - 1, l, i).se;
// cout << range[0][i] << '\n';
}
for(int k = 1; k < MAXK; k++){
for(int i = 0; i < n; i++){
range[k][i] = range[k - 1][range[k - 1][i]];
}
}
}
int solve(int a, int b){
if(vec[a].fi.se >= vec[b].fi.fi && vec[a].fi.se <= vec[b].fi.se){
return 1;
}
if(vec[a].fi.se > vec[b].fi.se){
return -1;
}
int res = 0;
int akt = b;
for(int i = MAXK - 1; i >= 0; i--){
int nr = range[i][akt];
if(vec[a].fi.se >= vec[nr].fi.fi){
continue;
}
res += (1 << i);
akt = nr;
if(vec[a].fi.se >= vec[akt].fi.fi && vec[a].fi.se <= vec[akt].fi.se){
return res + 1;
}
}
res++;
akt = range[0][akt];
if(vec[a].fi.se >= vec[akt].fi.fi && vec[a].fi.se <= vec[akt].fi.se){
return res + 1;
}
return -1;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> q;
for(int i = 1; i <= n; i++){
int s,e;
cin >> s >> e;
vec.pb({{e, s}, i});
}
sort(all(vec));
for(int i = 0; i < n; i++){
swap(vec[i].fi.fi, vec[i].fi.se);
pos[vec[i].se] = i;
}
preprocessing();
/*for(auto ele : vec){
cout << ele.fi.fi << ' ' << ele.fi.se << '\n';
}
for(int i = 0; i < n; i++){
for(int j = 0; j < MAXK / 2; j++){
cout << range[j][i] << ' ';
}
cout << '\n';
}*/
while(q--){
int s, e;
cin >> s >> e;
s = pos[s];
e = pos[e];
// cout << "PYTANIE: " << s << ' ' << e << '\n';
if(s == e){
cout << 0 << '\n';
continue;
}
int ans = solve(s, e);
if(ans == -1){
cout << "impossible\n";
}else{
cout << ans << '\n';
}
}
return 0;
}
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