#include <iostream> #include <vector> #include <algorithm> using namespace std; const int N = (1<<17) + 1; int Mn[N<<1], Mx[N<<1], num[N<<1]; void Add(int i, int v, int cur = 1, int st = 1, int en = N){ if (i >= en or i < st) return; if (en - st == 1){ num[cur] += v; if (num[cur] == 0) Mn[cur] = N, Mx[cur] = 0; else Mn[cur] = Mx[cur] = st; return; } int lc = cur + cur, rc = lc + 1, mid = (st + en) / 2; Add(i, v, lc, st, mid); Add(i, v, rc, mid, en); Mn[cur] = min(Mn[lc], Mn[rc]); Mx[cur] = max(Mx[lc], Mx[rc]); } int get1(int k, int cur = 1, int st = 1, int en = N){ if (en - st == 1) return st; int lc = cur + cur, rc = lc + 1, mid = (st + en) / 2; if (Mn[rc] <= k) return get1(k, rc, mid, en); return get1(k, lc, st, mid); } int get2(int k, int cur = 1, int st = 1, int en = N){ if (en - st == 1) return st; int lc = cur + cur, rc = lc + 1, mid = (st + en) / 2; if (Mx[lc] >= k) return get2(k, lc, st, mid); return get2(k, rc, mid, en); } int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); for (int i=1;i<(N<<1);i++) Mn[i] = N; int n; cin>>n; vector<pair<int,int>> vec; for (int i=1;i<=n;i++){ int h, k; cin>>h>>k; vec.push_back({h, k}); } sort(vec.begin(), vec.end()); Add(1, -1); Add(N - 2, -1); for (auto [h, k] : vec){ int f = get1(h - k + 1); int s = get2(h - k + 1) - 1; int l1 = h - min(h, s); // cout<<h<<" "<<k<<" "<<l1<<" "<<f<<" "<<s<<endl; Add(s + 1, 1); Add(s + l1 + 1, -1); Add(f, 1), Add(f + k - l1, -1); } Add(1, 1); long long Ans = 0; for (int i=1, sm = 0;i<=n;i++){ sm += num[131071 + i]; // cout<<sm<<'\n'; Ans += (1LL * sm * (sm - 1)) / 2; } cout<<Ans<<'\n'; }