#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
//typedef long double ld;
typedef pair<int, ll> pil;
//typedef pair<ld, int> pdi;
const int MAXN = 1e5;
int sails_avail[MAXN];
ll sails_above[MAXN];
pil points[MAXN];
int sortable[MAXN];
int n;
struct comp {
bool operator()(const int &a, const int &b) {
if (points[a].second*points[b].first == points[b].second*points[a].first) return points[a].first > points[b].first;
return points[a].second*points[b].first < points[b].second*points[a].first;
}
} comp;
ll area(pil &a, pil &b, pil &c) {
ll aval = a.first*b.second+b.first*c.second+c.first*a.second;
ll bval = a.second*b.first+b.second*c.first+c.second*a.first;
return abs(aval-bval);
}
bool contained(pil &a, pil &b, pil &c, pil &p) {
return (area(a, b, p) + area(a, c, p) + area(b, c, p) == area(a, b, c));
}
ll c2(ll a) {
return a*(a-1)/2;
}
ll ineff(ll y, int x) {
ll per = y/x;
int numgreat = y-x*per;
return (x-numgreat)*c2(per)+numgreat*c2(per+1);
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
cin >> n;
int mxh = 0;
for (int i = 0; i < n; i++) {
int h, k;
cin >> h >> k;
sails_avail[h-1]++;
mxh = max(mxh, h);
if (h > k) sails_avail[h-k-1]--;
}
ll d = 0;
ll cur = 0;
for (int i = mxh-1; i >= 0; i--) {
d += sails_avail[i];
cur += d;
sails_above[i] = cur;
}
for (int i = mxh-1; i >= 0; i--) {
points[i] = pil(mxh-i, sails_above[i]);
}
iota(sortable, sortable+mxh, 0);
sort(sortable, sortable+mxh, comp);
vector<pil> hull;
hull.push_back(pil(0, 0));
for (int i = 0; i < mxh; i++) {
pil cur = points[sortable[i]];
if (cur.first < hull.back().first) continue;
while (hull.size() > 2 && contained(cur, hull[0], hull[hull.size()-2], hull[hull.size()-1])) hull.pop_back();
hull.push_back(cur);
}
ll ans = 0;
for (int i = 1; i < hull.size(); i++)
ans += ineff(hull[i].second-hull[i-1].second, hull[i].first-hull[i-1].first);
cout << ans << "\n";
}
