#include<bits/stdc++.h>

 #define pa pair<ll,int>

 #define CLR(a,x) memset(a,x,sizeof(a))

 using namespace std;

 typedef long long ll;

 const int maxn=5e5+,maxp=maxn*,maxl=maxn*,P=1e9+;

 const ll inf=1e18+;

 inline ll rd(){

     ll x=;char c=getchar();int neg=;

     while(c<''||c>''){if(c=='-') neg=-;c=getchar();}

     while(c>=''&&c<='') x=x*+c-'',c=getchar();

     return x*neg;

 }

 int N;

 ll pos[maxn],r[maxn];

 int rg[maxn][],id[maxn],ch[maxp][],pct,root;

 int eg[maxl][],egh[maxp],ect;

 int eg2[maxl][],egh2[maxp],ect2,ine[maxp];

 int dfn[maxp],low[maxp],tot,stk[maxp],sh;

 int bel[maxp],nct,hav[maxp],hh[maxp];

 int val[maxp],rk[maxp];

 bool instk[maxp],islef[maxp],to[maxp];

 queue<int> q;

 inline void adeg(int a,int b){

     eg[++ect][]=b;eg[ect][]=egh[a];egh[a]=ect;

 }

 inline void adeg2(int a,int b){

     ine[b]++;

     eg2[++ect2][]=b;eg2[ect2][]=egh2[a];egh2[a]=ect2;

 }

 void build(int &p,int l,int r){

     p=++pct;

     if(l==r) id[l]=p,islef[p]=;

     if(l<r){

         int m=l+r>>;

         build(ch[p][],l,m);

         build(ch[p][],m+,r);

         adeg(p,ch[p][]),adeg(p,ch[p][]);

     }

 }

 void conn(int p,int l,int r,int x,int y,int z){

     if(x>y) return;

     if(x<=l&&r<=y){

         adeg(z,p);

     }else{

         int m=l+r>>;

         if(x<=m) conn(ch[p][],l,m,x,y,z);

         if(y>=m+) conn(ch[p][],m+,r,x,y,z);

     }

 }

 void tarjan(int x){

     dfn[x]=low[x]=++tot;

     stk[++sh]=x;instk[x]=;

     for(int i=egh[x];i;i=eg[i][]){

         int b=eg[i][];

         if(instk[b]) low[x]=min(low[x],dfn[b]);

         else if(!dfn[b]){

             tarjan(b);

             low[x]=min(low[x],low[b]);

         }

     }

     if(dfn[x]==low[x]){

         ++nct;

         while(sh){

             bel[stk[sh]]=nct;

             hav[stk[sh]]=hh[nct],hh[nct]=stk[sh];

             val[nct]+=islef[stk[sh]];

             instk[stk[sh]]=;

             sh--;

             if(stk[sh+]==x) break;

         }

     }

 }

 int main(){

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

     int i,j,k;

     N=rd();

     for(i=;i<=N;i++) pos[i]=rd(),r[i]=rd();

     for(i=;i<=N;i++){

         rg[i][]=lower_bound(pos+,pos+N+,pos[i]-r[i])-pos;

         rg[i][]=upper_bound(pos+,pos+N+,pos[i]+r[i])-pos-;

         // printf("%d %d %d\n",i,rg[i][0],rg[i][1]);

     }

     build(root,,N);

     for(i=;i<=N;i++){

         conn(root,,N,rg[i][],i-,id[i]);

         conn(root,,N,i+,rg[i][],id[i]);

     }

     for(i=;i<=pct;i++){

         if(!dfn[i]) tarjan(i);

     }

     for(i=;i<=nct;i++){

         for(j=hh[i];j;j=hav[j]){

             for(k=egh[j];k;k=eg[k][]){

                 int bb=bel[eg[k][]];if(bb==i) continue;

                 if(!to[bb]) adeg2(i,bb),to[bb]=;

             }

         }

         for(j=hh[i];j;j=hav[j]){

             for(k=egh[j];k;k=eg[k][]){

                 int bb=bel[eg[k][]];

                 to[bb]=;

             }

         }

     }

     int nn=;

     for(i=;i<=nct;i++){

         if(!ine[i]) q.push(i);

     }

     while(!q.empty()){

         int p=q.front();q.pop();

         rk[++nn]=p;

         for(i=egh2[p];i;i=eg2[i][]){

             int b=eg2[i][];

             if(--ine[b]==) q.push(b);

         }

     }

     for(i=nct;i;i--){

         int p=rk[i];

         for(j=egh2[p];j;j=eg2[j][]){

             int b=eg2[j][];

             val[p]+=val[b];

         }

     }

     ll ans=;

     for(i=;i<=N;i++){

         ans=(ans+1ll*i*val[bel[id[i]]])%P;

     }

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

     return ;

 }