#include <bits/stdc++.h>
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define len(a) int((a).size())
#define ll long long
#define name ""
using namespace std;
void fastio(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
}
void file(){
if(fopen(name ".inp", "r")){
freopen(name ".inp", "r", stdin);
freopen(name ".out", "w", stdout);
}
}
struct node{
int lz, mx, mn;
};
vector <node> st;
vector <pair <int, int>> a;
int n, mx_n;
void inp(){
cin >> n;
a.resize(n + 1);
for(int i = 1; i <= n; i++){
cin >> a[i].first >> a[i].second;
}
sort(a.begin() + 1, a.begin() + 1 + n);
mx_n = a[n].first;
st.assign(4*mx_n + 7, {0, 0, 0});
}
void down(int id){
int val = st[id].lz;
if(val == 0) return;
st[id].lz = 0;
st[2*id].lz += val;
st[2*id].mx += val;
st[2*id].mn += val;
st[2*id + 1].lz += val;
st[2*id + 1].mx += val;
st[2*id + 1].mn += val;
}
node get_in4(int id, int l, int r, int u, int v){
if(v < l || r < u) return {0, 0, (int)1e9};
if(u <= l && r <= v) return st[id];
down(id);
int mid = (l + r)/2;
node get1 = get_in4(2*id, l, mid, u, v);
node get2 = get_in4(2*id + 1, mid + 1, r, u, v);
return {0, max(get1.mx, get2.mx), min(get1.mn, get2.mn)};
}
int get_pos(int id, int l, int r, int u, int v, int val){
if(v < l || r < u) return -1;
if(st[id].mn > val) return -1;
if(l == r) return l;
down(id);
int mid = (l + r)/2;
int get1 = get_pos(2*id, l, mid, u, v, val);
if(get1 == -1) get1 = get_pos(2*id + 1, mid + 1, r, u, v, val);
return get1;
}
void update(int id, int l, int r, int u, int v){
if(v < l || r < u) return;
if(u <= l && r <= v){
st[id].lz += 1;
st[id].mx += 1;
st[id].mn += 1;
return;
}
down(id);
int mid = (l + r)/2;
update(2*id, l, mid, u, v);
update(2*id + 1, mid + 1, r, u, v);
st[id].mx = max(st[2*id].mx, st[2*id + 1].mx);
st[id].mn = min(st[2*id].mn, st[2*id + 1].mn);
}
int get_ans(int id, int l, int r, int pos){
if(pos < l || pos > r) return -1;
if(l == r) return st[id].mx;
down(id);
int mid = (l + r)/2;
int get1 = get_ans(2*id, l, mid, pos);
int get2 = get_ans(2*id + 1, mid + 1, r, pos);
return max(get1, get2);
}
ll calc(ll num){
return (num*(num+1))/2;
}
void solve(){
inp();
for(int i = 1; i <= n; i++){
int cur_pos = a[i].first - a[i].second + 1;
node in4 = get_in4(1, 1, mx_n, cur_pos, a[i].first);
if(in4.mx != in4.mn){
int pos = get_pos(1, 1, mx_n, 1, a[i].first, in4.mx - 1);
update(1, 1, mx_n, pos, a[i].first);
int rest = a[i].second - (a[i].first - pos + 1);
pos = get_pos(1, 1, mx_n, 1, a[i].first, in4.mx);
update(1, 1, mx_n, pos, pos + rest - 1);
}
else{
int pos = get_pos(1, 1, mx_n, 1, a[i].first, in4.mx);
update(1, 1, mx_n, pos, pos + a[i].second - 1);
}
}
ll ans = 0;
for(int i = 1; i <= mx_n; i++){
int num = get_ans(1, 1, mx_n, i);
ans += calc(1LL*num - 1);
}
cout << ans << '\n';
}
int main(){
fastio();
file();
solve();
return 0;
}
