#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#ifdef IOI
template<typename T>
void dbg(const T&t){
cout<<t<<endl;
}
template<typename T,typename... Args>
void dbg(const T& t,const Args&... args){
cout<<t<<" , ";
dbg(args...);
}
#define dbg(...) cout<<"("<<#__VA_ARGS__<<"): ";dbg(__VA_ARGS__);
#else
#define dbg(...) 1337;
#endif
#define F first
#define S second
const int maxn=1e5+100;
const int mod=1e9+7;
signed main(){
int n;
cin>>n;
vector<pair<int,int>> v(n);
for(int i=0;i<n;i++){
cin>>v[i].F>>v[i].S;
}
int dp[n];
int t=sqrt(n)+1;
vector<vector<int>> cnt(n,vector<int>(t+2,0));
memset(dp,0,sizeof(dp));
for(int i=n-1;i>=0;i--){
dp[i]=1;
int a=v[i].F;
int b=v[i].S;
if(a==0||b==0) {
for(int j=1;j<=t;j++) {
cnt[i][j]=dp[i];
if(i+j<n) cnt[i][j]+=cnt[i+j][j];
cnt[i][j]%=mod;
}
continue;
}
if(a<=t){
if(i+a<n)
dp[i]+=cnt[i+a][a];
dp[i]%=mod;
if(i+b*a+b<n) dp[i]-=cnt[i+b*a+b][a];
dp[i]%=mod;
if(dp[i]<0) dp[i]+=mod;
}else{
int j=i;
b--;j+=a;
while(b>=0){
if(j>n) break;
dp[i]+=dp[j];
dp[i]%=mod;
b--,j+=a;
}
}
for(int j=1;j<=t;j++) {
cnt[i][j]=dp[i];
if(i+j<n) cnt[i][j]+=cnt[i+j][j];
cnt[i][j]%=mod;
}
}
dp[0]%=mod;
if(dp[0]<0) dp[0]+=mod;
cout<<dp[0]<<endl;
}
