#include <bits/stdc++.h>
#define ss second
#define pb push_back
#define mod 998244353
#define N 100005
#define INF 1000000000000000005
#define pu push
#define ff first
#define pint pair<int,int>
using namespace std;
int n,go[N][325];
pint arr[N];
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin>>n;
for(int i=0;i<n;i++)
{
cin>>arr[i].ff>>arr[i].ss;
}
int ans[n],sum=0;
memset(ans,0,sizeof(ans));
ans[0]=1;
for(int i=0;i<n;i++)
{
for(int j=1;j<322;j++)
{
ans[i]+=go[i][j];
}
sum+=ans[i];
if(arr[i].ff>320)
{
int ind=arr[i].ff+1;
while(ind<n&&arr[i].ss)
{
ans[ind]+=ans[i];
arr[i].ss--;
}
}
else
{
go[i][arr[i].ff]+=ans[i];
if(i+arr[i].ff*(arr[i].ss+1)<n)
go[i+arr[i].ff*(arr[i].ss+1)][arr[i].ff]-=ans[i];
}
for(int j=1;j<322;j++)
{
if(i+j>=n)
break;
go[i+j][j]+=go[i][j];
}
}
cout<<sum<<endl;
return 0;
}
