#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define pb push_back
#define sz(a) (ll) a.size()
#define all(x) (x).begin(), (x).end()
#define rep(i, a, b) for(ll i=a; i<b; i++)
#define rrep(i, a, b) for(ll i=a; i>=b; i--)
#define vl vector<ll>
#define vpll vector<pair<ll, ll>>
#define vvl vector<vector<ll>>
#define pll pair<ll, ll>
ll n;
vl l, r;
void f() {
cin >> n;
if(n==0){
cout << 0;
return;
}
l.resize(n);
r.resize(n);
rep(i, 0, n) cin >> l[i] >> r[i];
cout << (ll)((n+l[0])/(l[0]+1));
}
int main() {
int tc = 1;
// cin >> tc;
for (int i = 1; i <= tc; i++) {
// cout << '#' << i << endl;
f();
// if (i != tc) cout << endl;
}
}
