#include <bits/stdc++.h> using namespace std; // #include <ext/pb_ds/assoc_container.hpp> // #include <ext/pb_ds/tree_policy.hpp> // using namespace __gnu_pbds; typedef long long ll; typedef long double ld; typedef pair<int, int> pii ; typedef pair<ll, ll> pll ; typedef vector<pii> vii ; typedef vector<int> veci ; typedef vector<pll> vll ; typedef vector<ll> vecll; // find_by_order order_of_key //#pragma GCC optimize("O3,unroll-loops") //#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt") #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> #define F first #define S second #define pb push_back #define endl '\n' #define Mp make_pair #define all(x) x.begin(), x.end() #define debug(x) cerr << #x << " = " << x << endl #define set_dec(x) cout << fixed << setprecision(x); #define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define file_io freopen("in.txt" , "r" , stdin) ; freopen("out.txt" , "w" , stdout); #define lb lower_bound #define ub upper_bound #define for1(n) for(int i=1;i<=n;i++) #define for0(n) for(int i=0;i<n;i++) #define forn(n) for(int i=n;i>0;i--) #define pq priority_queue <pii, vector<pii>, greater<pii>> const int mod=1e9+7; const int N=1e5+3; int n,m,k,q; ll dp[N]; map<int,int>C[N]; int main(){ fast_io cin>>n; dp[1]=1; ll ans=0; for1(n){ dp[i]%=mod; ans+=dp[i]; int x,y;cin>>x>>y; if(x!=0){ C[i][x]=(C[i][x]+dp[i])%mod; if(ll(i)+1ll*x*y<=n) C[i+x*y][x]=(C[i+x*y][x]+mod-dp[i])%mod; } for(pii p:C[i])if(p.S!=0){ if(i+p.F<=n){ C[i+p.F][p.F]=(C[i+p.F][p.F]+p.S)%mod; dp[i+p.F]+=p.S; } } } cout<<ans%mod<<endl; }