#include<bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(false);cin.tie(NULL)
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define eb emplace_back
#define pre(a) cout<<fixed; cout.precision(a)
#define mp make_pair
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const long long INF = 1e18;
const int inf = 1e9;
int n;
vector<pii> v;
vector<int> x;
int tree[101010];
ll ans;
void update(int i, int x) {
while(i <= 100010) {
tree[i] += x;
i += i & -i;
}
}
int get(int i) {
if(i == 0) return inf;
int ret = 0;
while(i) {
ret += tree[i];
i -= i & -i;
}
return ret;
}
int f(int x) {
return -x*x;
}
int main() {
fast;
cin >> n;
for(int i=0; i<n; i++) {
int h, k;
cin >> h >> k;
v.eb(h, k);
}
for(int i=0; i<=100010; i++) {
x.eb(i);
}
sort(all(v));
for(auto i : v) {
int lb = lower_bound(all(x), i.fi - i.se + 1, [](int a, int b) { return get(a) > get(b); }) - x.begin();
int ub = upper_bound(all(x), i.fi - i.se + 1, [](int a, int b) { return get(a) > get(b); }) - x.begin();
int k = i.se;
if(ub <= i.fi) {
update(ub, 1);
update(i.fi+1, -1);
k -= i.fi + 1 - ub;
}
update(lb, 1);
update(lb + k, -1);
}
for(int i=1; i<=100010; i++) {
ll t = get(i);
ans += t * (t-1)/2;
}
cout << ans;
}
