#include<bits/stdc++.h>
using namespace std;
// define
#define execute cerr << " Time: " << fixed << setprecision(6) << (1.0 * clock() / CLOCKS_PER_SEC) << "s\n";
#define ll long long
#define int long long
#define ld double
#define ii pair<int,int>
#define se second
#define fi first
#define iii pair<int,ii>
#define all(v) v.begin(),v.end()
#define bit(x,i) (((x)>>(i))&1LL)
#define flip(x,i) ((x)^(1LL<<(i)))
#define ms(d,x) memset(d,x,sizeof(d))
#define sitingfake 1
#define orz 1
//constant
const ll mod = 1e9 + 7;
const long long linf = 4557430888798830399;
const int inf = 1061109567;
const int maxarr = 1e6 + 5;
const int dx[] = {0,1,-1,0};
const int dy[] = {1,0,0,-1};
template<typename T> bool maximize(T &a, const T &b)
{
if(a < b) {a = b; return 1;}
return 0;
}
template<typename T> bool minimize(T &a, const T &b)
{
if(a > b) {a = b; return 1;}
return 0;
}
inline void Plus(ll & a ,ll b)
{
b %= mod;
a += b;
if(a >= mod) a -= mod;
if(a < 0) a += mod;
return;
}
inline void Mul(ll & a, ll b)
{
a %= mod; b %= mod;
a *= b;
a %= mod;
return;
}
//code
const int maxn = 1e5 + 7;
const int Lim = 1e5;
ii a[maxn];
int bit[maxn];
int n;
void up(int x , int val)
{
for(; x <= Lim ; x += (x & -x))
{
bit[x] += val;
}
}
int get(int x)
{
int ans = 0;
for(;x > 0 ; x -= (x & -x))
{
ans += bit[x];
}
return ans;
}
int search(int x , int val)
{
int l = 1 , r = x , ans = x + 1;
while(l <= r)
{
int mid = (r + l) >> 1;
if(get(mid) < val)
{
ans = mid;
r = mid - 1;
}
else l = mid + 1;
}
return ans;
}
void solve(void)
{
cin >> n;
for(int i = 1; i <= n; i++)
{
cin >> a[i].fi >> a[i].se;
}
sort(a + 1, a + n + 1);
for(int i = 1; i <= n ; i++)
{
int val = get(a[i].fi - a[i].se);
int l = search(a[i].fi , val);
if(l != a[i].fi + 1)
{
up(l , 1);
up(a[i].fi + 1 , -1);
}
int L = search(a[i].fi , val + 1);
up(L , 1);
up(L + a[i].se - (a[i].fi - l + 1) , -1);
}
ll ans = 0;
for(int i = 1; i <= a[n].fi ; i++)
{
ll val = get(i);
ans += (val * (val - 1)) / 2;
}
cout << ans;
}
/**
**/
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
#define task ""
if(fopen(task".inp","r"))
{
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
int tc; tc = 1;
while(tc--) solve();
//execute;
}
