#include <bits/stdc++.h> // mrrrowwww meeowwwww :3 // go play vivid/stasis! !! !!! https://vividstasis.gay #define fo(i, a, b) for (auto i = (a); i < (b); i++) #define of(i, a, b) for (auto i = (b); i-- > (a);) #define f first #define s second #define pb push_back #define lb lower_bound #define ub upper_bound #define be(a) a.begin(), a.end() using namespace std; int ____init = []{ ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); return 0; }(); int a[100001]; int bit[100002]; int get(int i) { int res = 0; for (i++; i > 0; i -= i & -i) res += bit[i]; return res; } void add(int i, int v) { a[i] += v; for (i++; i <= 100000; i += i & -i) bit[i] += v; } int main() { int n; cin >> n; int max_h = 0; fo(_, 0, n) { int h, k; cin >> h >> k; max_h = max(max_h, h); add(h, -1); if (a[h - k]) { add(h - k, 1); } else { int start_hk = get(h - k); int l = 0, r = h - k; while (l < r) { int mid = (l + r) / 2; if (get(mid) != start_hk) l = mid + 1; else r = mid; } int hk_left = l; l = h - k, r = h; while (l < r) { int mid = (l + r) / 2; if (get(mid) != start_hk) r = mid; else l = mid + 1; } int hk_right = l; add(hk_left, 1); add(hk_left + hk_right - (h - k), -1); add(hk_right, 1); } } long long res = 0; int acc = 0; fo(i, 0, max_h) acc += a[i], res += (long long) acc * (acc - 1) / 2; cout << res; }