#include <bits/stdc++.h>
#define IO_OP std::ios::sync_with_stdio(0); std::cin.tie(0);
#define F first
#define S second
#define V vector
#define PB push_back
#define MP make_pair
#define EB emplace_back
#define ALL(v) (v).begin(), (v).end()
#define debug(x) cerr << "Line(" << __LINE__ << ") -> " << #x << " is " << x << endl
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
const int INF = 1e9 + 7, N = 1e5 + 7;
struct node {
int mx, lz;
node(int val = 0) {
mx = val;
lz = 0;
}
};
node t[N * 4];
void apply(int v, int val) {
t[v].mx += val;
t[v].lz += val;
}
void push(int v) {
apply(v * 2, t[v].lz);
apply(v * 2 + 1, t[v].lz);
t[v].lz = 0;
}
void add(int l, int r, int val, int v = 1, int tl = 0, int tr = N) {
if(l <= tl && tr <= r) {
apply(v, val);
return;
}
push(v);
int tm = (tl + tr) / 2;
if(l < tm) add(l, r, val, v * 2, tl, tm);
if(r > tm) add(l, r, val, v * 2 + 1, tm, tr);
t[v].mx = max(t[v * 2].mx, t[v * 2 + 1].mx);
}
int qry(int pos, int v = 1, int tl = 0, int tr = N) {
if(tr - tl == 1)
return t[v].mx;
push(v);
int tm = (tl + tr) / 2;
if(pos < tm) return qry(pos, v * 2, tl, tm);
else return qry(pos, v * 2 + 1, tm, tr);
}
int find_first_geq(int val, int v = 1, int tl = 0, int tr = N) {
if(tr - tl == 1) {
if(t[v].mx >= val) return tl;
else {
assert(tl == N - 1);
return N;
}
}
push(v);
int tm = (tl + tr) / 2;
if(t[v * 2].mx >= val) return find_first_geq(val, v * 2, tl, tm);
else return find_first_geq(val, v * 2 + 1, tm, tr);
}
ll c(int n) {
return (ll) n * (n - 1) / 2;
}
ll ans(int v = 1, int tl = 0, int tr = N) {
if(tr - tl == 1) {
return c(t[v].mx);
}
push(v);
int tm = (tl + tr) / 2;
return ans(v * 2, tl, tm) + ans(v * 2 + 1, tm, tr);
}
signed main()
{
IO_OP;
int n;
cin >> n;
V<pi> v(n);
for(int i = 0; i < n; i++) cin >> v[i].F >> v[i].S;
sort(ALL(v));
for(int i = 0; i < n; i++) {
int L = N - v[i].F;
int R = L + v[i].S - 1;
int val_r = qry(R);
int l = max(find_first_geq(val_r), L);
int r = max(find_first_geq(val_r + 1), L);
int take_r = R - l + 1;
if(L < l) add(L, l, 1);
add(r - take_r, r, 1);
}
cout << ans() << '\n';
}
