/******************************************************************************
Online C++ Compiler.
Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.
*******************************************************************************/
#include <iostream>
using namespace std;
int n,x[100005],d[100005],sum[100005];
int main()
{
cin>>n;
for (int i = 1; i <= n; i++){
cin>>d[i]>>x[i];
}
sum[1] = 1;
for (int i = 1; i<=n;i++){
while (d[i] == 0 && i <= n){
i++;
}
if (i > n)
break;
int p = i + d[i];
while (x[i]){
if (p <= n)
sum[p] += sum[i];
else
break;
if (p + d[i] <= n)
p += d[i];
else
break;
x[i]--;
}
}
int suma = 0;
for (int i = 1; i <=n; i++){
suma += sum[i];
}
cout << suma;
return 0;
}
