#include <cstdio>
#include <iostream>
#include <vector>
#include <list>
#include <string>
#include <set>
#include <map>
#include <algorithm>
#include <fstream>
#include <cmath>
#include <queue>
#include <stack>
#include <cassert>
#include <cstring>
#include <climits>
#include <functional>
#include<cstdlib>
//#include "arc.h"
using namespace std;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef long long LL;
const int INF = 2147483640;
const int MAXN = 2e5 + 111;
const int MAXS = 1e5 + 111;
const long long P = 31;
using ll = long long;
const ll mod1 = 1e9 + 7;
const ll mod2 = 998244353;
int n;
ll lazy[4 * MAXN];
ll t[4 * MAXN];
ll ans;
pair<int, int> arr[MAXN];
ll get_sum(ll N)
{
return (N * (N + 1)) / 2;
}
void push(int v) {
t[v * 2] += lazy[v];
lazy[v * 2] += lazy[v];
t[v * 2 + 1] += lazy[v];
lazy[v * 2 + 1] += lazy[v];
lazy[v] = 0;
}
void update(int v, int tl, int tr, int l, int r, ll addend) {
if (l > r)
return;
if (l == tl && tr == r) {
t[v] += addend;
lazy[v] += addend;
}
else {
push(v);
int tm = (tl + tr) / 2;
update(v * 2, tl, tm, l, min(r, tm), addend);
update(v * 2 + 1, tm + 1, tr, max(l, tm + 1), r, addend);
t[v] = max(t[v * 2], t[v * 2 + 1]);
}
}
ll query(int v, int tl, int tr, int l, int r) {
if (l > r)
return -INF;
if (l == tl && tr == r)
return t[v];
push(v);
int tm = (tl + tr) / 2;
return max(query(v * 2, tl, tm, l, min(r, tm)),
query(v * 2 + 1, tm + 1, tr, max(l, tm + 1), r));
}
int first_element(int x,int lim)
{
int l = 1, r = lim;
while (l < r)
{
int m = (l + r + 1) / 2;
if (query(1, 0, MAXN, m, lim) >= x)
l = m;
else
r = m - 1;
}
return l;
}
int last_element(int x,int lim)
{
int l = 1, r = lim;
while (l < r)
{
int m = (l + r) / 2;
if (query(1, 0, MAXN, m, lim) > x)
l = m + 1;
else
r = m;
}
return l;
}
int main() {
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(0);
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> arr[i].first >> arr[i].second;
}
sort(arr + 1, arr + 1 + n);
for (int i = 1; i <= n; i++)
{
int H = arr[i].first;
int K = arr[i].second;
int last_mast = H - K + 1;
int ele = query(1, 0, MAXN, last_mast, last_mast);
int L = last_element(ele, H);
int F = first_element(ele, H);
if (L == last_mast)
{
update(1, 0, MAXN, last_mast, H, 1);
}
else
{
//cout << F << " " << L << " " << ele << " XX " << k[i] << '\n';
update(1, 0, MAXN, F + 1, H, 1);
int rest = K - (H - (F + 1) + 1);
update(1, 0, MAXN, L, L + rest - 1, 1);
}
}
for (int i = 1; i <= (int)2e5; i++)
{
ans += get_sum(max(0ll,query(1, 0, MAXN, i, i)-1));
}
cout<<ans<<'\n';
return 0;
}
