#include <bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 1000000007
#define LOGN 7
#define MAXN 100005
vector<pair<int,int>> mast;
int sg[4*MAXN], lazy[4*MAXN];
void update(int k, int a, int b, int q_l, int q_r) {
if (lazy[k]) {
sg[k] += (b-a+1) * lazy[k];
if (a != b) {
lazy[2*k] += lazy[k];
lazy[2*k+1] += lazy[k];
}
lazy[k] = 0;
}
if (q_l > b || q_r < a)
return ;
if (q_l <= a && b <= q_r) {
sg[k] += b-a+1;
if (a != b) {
lazy[2*k]++;
lazy[2*k+1]++;
}
return ;
}
update(2*k, a, (a+b)/2, q_l, q_r);
update(2*k+1, (a+b)/2+1, b, q_l, q_r);
sg[k] = sg[2*k] + sg[2*k+1];
}
int get(int k, int a, int b, int plc) {
if (lazy[k]) {
sg[k] += (b-a+1) * lazy[k];
if (a != b) {
lazy[2*k] += lazy[k];
lazy[2*k+1] += lazy[k];
}
lazy[k] = 0;
}
if (plc < a || plc > b)
return 0;
if (a == b)
return sg[k];
return get(2*k, a, (a+b)/2, plc) + get(2*k+1, (a+b)/2+1, b, plc);
}
int main() {
fast
int N;
cin >> N;
mast = vector<pair<int,int>>(N);
for (int i = 0; i < N; i++)
cin >> mast[i].f >> mast[i].s;
sort(mast.begin(), mast.end());
for (int i = 0; i < N; i++) {
int h = mast[i].f, k = mast[i].s;
int left = 100001 - h;
int plc = get(1, 1, 100000, left + k - 1);
int L = left, R = 100000;
int ans = -1;
while (R >= L) {
int mid = L + (R-L)/2;
if (get(1, 1, 100000, mid) < plc) {
ans = mid;
L = mid + 1;
} else
R = mid - 1;
}
L = left, R = 100000;
int last_pos = -1;
while (R >= L) {
int mid = L + (R-L)/2;
if (get(1, 1, 100000, mid) <= plc) {
last_pos = mid;
L = mid + 1;
} else
R = mid - 1;
}
if (ans != -1) {
update(1, 1, 100000, left, ans);
k -= ans - left + 1;
}
if (k)
update(1, 1, 100000, last_pos - k + 1, last_pos);
}
ll ans = 0;
for (int i = 1; i <= 100000; i++) {
ll q = get(1, 1, 100000, i);
ans += q * (q-1) / 2;
}
cout << ans << "\n";
}
