#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#define ll long long
#define pii pair<int,int>
#define piii pair<pii,int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define endl "\n"
#define all(a) a.begin(),a.end()
#define int long long
const int mod=1e9+7,C=400;
void solve(){
int n,ans=0;
cin>>n;
vector<int> d(n),x(n),dp(n);
vector<vector<int>> add(n,vector<int>(C+1));
dp[0]=1;
for(int i=0;i<n;i++){
cin>>d[i]>>x[i];
for(int j=1;j<=C;j++){
(dp[i]+=add[i][j])%=mod;
if(i+j<n) (add[i+j][j]+=add[i][j])%=mod;
}
(ans+=dp[i])%=mod;
if(i+d[i]>=n||x[i]==0||d[i]==0) continue;
if(d[i]<=C){
(add[i+d[i]][d[i]]+=dp[i])%=mod;
if(i+d[i]*(x[i]+1)<n) (add[i+d[i]*(x[i]+1)][d[i]]+=mod-dp[i])%=mod;
}
else{
for(int j=i+d[i];j<=min(n-1,i+d[i]*x[i]);j+=d[i]) (dp[j]+=dp[i])%=mod;
}
}
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int t=1;
//cin>>t;
while(t--){
solve();
}
return 0;
}
