#include<cstdio>

#include<iostream>

#include<cstring>

#include<cstdlib>

#include<algorithm>

#include<cmath>

using namespace std;

typedef long long LL;

struct trnode

{

    int f,son[],c,d,s;

}tr[];int trlen,root,cnt;

void update(int x)

{

    int lc=tr[x].son[],rc=tr[x].son[];

    tr[x].c=tr[lc].c+tr[rc].c+;

    tr[x].s=tr[lc].s+tr[rc].s+tr[x].d;

}

void rotate(int x,int w)

{

    int f=tr[x].f,ff=tr[f].f;

    int R,r;

    R=f,r=tr[x].son[w];

    tr[R].son[-w]=r;

    if(r!=)tr[r].f=R;

    R=ff,r=x;

    if(ff!=)

    {

        if(tr[R].son[]==f)tr[R].son[]=x;

        else tr[R].son[]=x;

    }

    tr[r].f=R;

    R=x,r=f;

    tr[R].son[w]=r;

    tr[r].f=R;

    update(f);

    update(x);

}

void splay(int x,int rt)

{

    while(tr[x].f!=rt)

    {

        int f=tr[x].f,ff=tr[f].f;

        if(ff==rt)

        {

            if(tr[f].son[]==x)rotate(x,);

            else rotate(x,);

        }

        else

        {

                  if(tr[f].son[]==x&&tr[ff].son[]==f){rotate(f,);rotate(x,);}

            else if(tr[f].son[]==x&&tr[ff].son[]==f){rotate(f,);rotate(x,);}

            else if(tr[f].son[]==x&&tr[ff].son[]==f){rotate(x,);rotate(x,);}

            else if(tr[f].son[]==x&&tr[ff].son[]==f){rotate(x,);rotate(x,);}

        }

    }

    if(x!=)

    {

        update(x);

        if(rt==)root=x;

    }

}

//~~~~~~~~~~~~~~~~~~~~~~~in~~~~~~~~~~~~~~~~~~~~~~~~~~~~

int FindFront()

{

    int f=root;

    while(tr[f].son[]!=)f=tr[f].son[];

    return f;

}

int FindBehind()

{

    int f=root;

    while(tr[f].son[]!=)f=tr[f].son[];

    return f;

}

int findkth(int k)

{

    int x=root;k++;

    if(k==)return ;

    while()

    {

        int lc=tr[x].son[],rc=tr[x].son[];

        if(tr[lc].c>=k)x=lc;

        else if(tr[lc].c+<k)k-=tr[lc].c+,x=rc;

        else return x;

    }

}

//~~~~~~~~~~~~~~~~~~~~Find~~~~~~~~~~~~~~~~~~~~~~~~~~~~

void add(int d,int f,int w)

{

    int x=++trlen;

    tr[x].f=f;tr[x].c=;tr[x].d=d;tr[x].s=d;

    tr[x].son[]=tr[x].son[]=;

    if(f!=)tr[f].son[w]=x;

}

void InsInFront(int d)

{

    if(root==)add(d,,),root=trlen;

    else add(d,FindFront(),);

    splay(trlen,);

}

void InsInBehind(int d)

{

    if(root==)add(d,,),root=trlen;

    else add(d,FindBehind(),);

    splay(trlen,);

}

void del(int x)

{

    splay(x,);

         if(tr[x].son[]==&&tr[x].son[]==)root=;

    else if(tr[x].son[]!=&&tr[x].son[]==){root=tr[x].son[];tr[root].f=;}

    else if(tr[x].son[]==&&tr[x].son[]!=){root=tr[x].son[];tr[root].f=;}

    else

    {

        int y=tr[x].son[];

        while(tr[y].son[]!=)y=tr[y].son[];

        splay(y,x);

        int R=y,r=tr[x].son[];

        tr[R].son[]=r;

        tr[r].f=R;

        root=y;tr[root].f=;

        update(y);

    }

}

//~~~~~~~~~~~~~~~~~~~~~~~out~~~~~~~~~~~~~~~~~~~~~~~~~

//-----------------------------------------------------------------------------------------------

LL ans,cc;

void dfs(int x)

{

    if(tr[x].son[]!=)dfs(tr[x].son[]);

    ans+=(cc-)*cc/*tr[x].d;cc++;

    if(tr[x].son[]!=)dfs(tr[x].son[]);

}

struct node{int h,k;}a[];

bool cmp(node n1,node n2){return n1.h<n2.h;}

int main()

{

    freopen("a.in","r",stdin);

    freopen("a.out","w",stdout);

    int n;

    scanf("%d",&n);

    for(int i=;i<=n;i++)

        scanf("%d%d",&a[i].h,&a[i].k);

    sort(a+,a+n+,cmp);

    a[].h=;

    trlen=,root=;

    tr[].f=;tr[].c=;tr[].d=;tr[].s=;

    tr[].son[]=tr[].son[]=;

    InsInFront();cnt=;

    for(int i=;i<=n;i++)

    {

        int fr=FindFront();

        tr[fr].d+=a[i].h-a[i-].h;

        splay(fr,);

        int l=,r=cnt,k;

        while(l<=r)

        {

            int mid=(l+r)/;

            int x=findkth(mid);splay(x,);

            if(tr[tr[x].son[]].s+tr[x].d>=a[i].k)

            {

                r=mid-;

                k=mid;

            }

            else l=mid+;

        }

        int x=findkth(k-);splay(x,);

        int s2=a[i].k-tr[tr[x].son[]].s-tr[x].d;//送给后一个点的值

        if(k==cnt)cnt++,InsInBehind(s2);

        else

        {

            int y=findkth(k+);

            tr[y].d+=s2;splay(y,);

        }

        x=findkth(k);

        int s1=tr[x].d-s2;//留给自己的值

        del(x);InsInFront();

        x=findkth(k);

        tr[x].d+=s1;splay(x,);

    }

    ans=;cc=;dfs(root);

    printf("%lld\n",ans);

    return ;

}