# include <iostream>
# include <algorithm>
using namespace std;
const int MAX=1e5+11;
int n,m=1e5;
pair<int,int> a[MAX];
long long tree[MAX*4];
long long lazy[MAX*4];
void push_lazy(int v, int l, int r)
{
if(lazy[v]==0) return ;
tree[v]+=lazy[v]*(r-l+1);
if(l!=r)
{
lazy[v*2]+=lazy[v];
lazy[v*2+1]+=lazy[v];
}
lazy[v]=0;
}
void update(int le, int ri, int d, int v=1, int l=1, int r=m)
{
push_lazy(v,l,r);
if(ri<l or r<le) return ;
if(le<=l and r<=ri)
{
lazy[v]+=d;
push_lazy(v,l,r);
return ;
}
int mid=(l+r)/2;
update(le,ri,d,v*2,l,mid);
update(le,ri,d,v*2+1,mid+1,r);
tree[v]=tree[v*2]+tree[v*2+1];
}
long long query(int le, int ri, int v=1, int l=1, int r=m)
{
push_lazy(v,l,r);
if(ri<l or r<le) return 0;
if(le<=l and r<=ri) return tree[v];
int mid=(l+r)/2;
return query(le,ri,v*2,l,mid)+query(le,ri,v*2+1,mid+1,r);
}
long long ans=0;
void perform(int l, int r)
{
ans+=query(l,r);
update(l,r,1);
//cout<<"->"<<l<<" "<<r<<"\n";
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin>>n;
for(int i=1;i<=n;i++) cin>>a[i].first>>a[i].second;
sort(a+1,a+n+1);
int last=1;
for(int i=1;i<=n;i++)
{
int all=a[i].first,left=a[i].second;
if(last+left-1>=all)
{
perform(last,all);
left-=(all-last+1);
last=1;
}
if(left>0)
{
perform(last,last+left-1);
last=last+left;
}
}
cout<<ans<<"\n";
return 0;
}
