#include "bits/stdc++.h"
using namespace std;
#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif
const int maxn = 1e5 + 5;
int n;
pair<int, int> a[maxn];
long long bit[maxn];
int cnt[maxn];
void update(int i, int x) {
for (; i < maxn; i += i & (-i)) {
bit[i] += x;
}
}
int get(int i) {
long long ans = 0;
for (; i > 0; i -= i & (-i)) {
ans += bit[i];
}
return ans;
}
void upd(int l, int r) {
if (l > r) return;
update(l, 1);
update(r + 1, -1);
}
void solve() {
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + n + 1);
int lim = 0;
for (int i = 1; i <= n; ++i) {
if (lim + a[i].second <= a[i].first) {
upd(lim + 1, lim + a[i].second);
lim += a[i].second;
continue;
}
if (lim < a[i].first) {
a[i].second -= a[i].first - lim;
upd(lim + 1, a[i].first);
}
int deg = get(lim - a[i].second + 1);
int l = 1, r = lim, pl = -1;
while (l <= r) {
int mid = (l + r) >> 1;
if (get(mid) >= deg) {
pl = mid;
l = mid + 1;
} else {
r = mid - 1;
}
}
l = 1, r = lim;
int pr = -1;
while (l <= r) {
int mid = (l + r) >> 1;
if (get(mid) <= deg) {
pr = mid;
r = mid - 1;
} else {
l = mid + 1;
}
}
upd(pl + 1, lim);
a[i].second -= lim - pl;
// debug(i, lim, pl, pr, deg, a[i]);
upd(pr, pr + a[i].second - 1);
lim = a[i].first;
}
long long res = 0;
for (int i = 1; i <= lim; ++i) {
int x = get(i);
res += 1ll * x * (x - 1) / 2;
}
cout << res;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
