#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define rep(a,b) for(int a = 0; a < (b); ++a)
#define all(t) t.begin(), t.end()
#define pb push_back
const int N = 1e5+5, INF = 2e9+54321, mod = 1e9+7, K = 317;
const ll INF_L = (ll)2e18+54321;
int n, wyn;
int D[N], X[N], dp[N], S[K][N];
void solve()
{
cin >> n;
rep(i,n) cin >> D[i] >> X[i];
wyn = 0, dp[0] = 1;
rep(i,n)
{
for(int j = 1; j < K; ++j) if(i-j >= 0) S[j][i] = (S[j][i]+S[j][i-j]) % mod;
for(int j = 1; j < K; ++j) dp[i] = (dp[i]+S[j][i]) % mod;
wyn = (wyn+dp[i]) % mod;
if(D[i] >= K)
{
for(int j = 1; j <= X[i] and (ll)i+(ll)j*D[i] < (ll)n; ++j)
{
dp[i+j*D[i]] = (dp[i+j*D[i]]+dp[i]) % mod;
}
}
else
{
S[D[i]][i] = (S[D[i]][i]+dp[i]) % mod;
S[D[i]][min((ll)n,(ll)i+(ll)(X[i]+1)*D[i])] = (S[D[i]][min((ll)n,(ll)i+(ll)(X[i]+1)*D[i])]-dp[i]+mod) % mod;
}
/*cout << '\n' << '\n';
cout << "I: " << i << " DP: " << dp[i] << '\n';
for(int j = 0; j <= 10; ++j) cout << "J: " << j << " S: " << S[j][i] << '\n';
cout << '\n' << '\n';*/
}
cout << wyn << '\n';
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int T = 1;
//cin >> T;
while(T--) solve();
return 0;
}
