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#include <bits/stdc++.h>
using namespace std;

#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define ff first
#define ss second

using ll = long long;
using pii = pair<int, int>;

template<class T> int size(T && a) {
	return (int)(a.size());
}
ostream& operator << (ostream &os, string str) {
    for(char c : str) os << c;
    return os;
}
template <class A, class B> ostream& operator << (ostream &os, const pair<A, B> &p) {
	return os << '(' << p.ff << "," << p.ss << ')';
}
template <class T> auto operator << (ostream &os, T &&x) -> decltype(x.begin(), os) {
	os << '{';
	for(auto it = x.begin(); it != x.end(); ++it)
		os << *it << (it == prev(x.end()) ? "" : " ");
	return os << '}';
}
template <class T> ostream& operator << (ostream &os, vector<vector<T>> vec) {
    for(auto x : vec)
    	os << "\n  " << x;
    return os;
}
void dump() {}
template <class T, class... Args> void dump(T &&x, Args... args) {
    cerr << x << "; ";
    dump(args...);
}
#ifdef DEBUG
# define debug(x...) cerr << "[" #x "]: ", dump(x), cerr << '\n'
#else 
# define debug(...) 0
#endif

//--------------------------------------------------

struct Mine {
	int a, r;
};

int n;
vector<Mine> mines;

int simulate(int mask) { //maska wybuchnietych bomb
	queue<int> Q;
	REP(i, n) {
		if((1 << i) & mask) {
			Q.push(i);
		}
	}

	int ret = mask;
	while(!Q.empty()) {
		int id = Q.front();
		Q.pop();

		REP(i, n) {
			if(abs(mines[id].a-mines[i].a) <= mines[id].r and (ret & (1 << i)) == 0) {
				ret |= (1 << i);
				Q.push(i);
			}
		}
	}
	return ret;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	cin >> n;
	mines.resize(n);
	REP(i, n) {
		cin >> mines[i].a >> mines[i].r;
	}

	set<int> S;
	REP(mask, (1<<n)) {
		S.insert(simulate(mask));
	}
	cout << size(S) << '\n';
}