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#include<bits/stdc++.h>
#define VAR(i,n) __typeof(n) i = (n)
#define loop(i,j,s) for(int i=j;i<s;i++)
#define loopback(i,j,s) for(int i=j;i>=s;i--)
#define foreach(i,c) for(VAR(i,(c).begin());i!=(c).end();i++)
#define pln( x ) cout << x << "\n"
#define ps( x ) cout << x << " "
#define entr cout << "\n"
#define pcnt(i) __builtin_popcount(i)
#define ll long long
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define SIZE(c) (c).size()
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef vector<vector<int> > VVI;
const int INFTY=20000000;
const int MAX=300100;
const int MOD=10000000;

void coutTab(int* tab,int n){
	loop(i,0,n){
		cout<<tab[i]<<" ";
	}
	cout<<"\n";
}

template<class T> void coutVec(vector<T> tab){
	for(T t : tab){
		cout<<t<<" ";
	}
	cout<<"\n";
}
//------------------------------------------
VVI G(MAX);
VVI GT(MAX);
VVI SCC(MAX);

VVI GC(MAX);

ll a[MAX];
ll r[MAX];

int n;
 
int order[MAX];
bool visited[MAX];
int rSCC[MAX];
 
void dfs1(int v){
	visited[v] = 1;
	static int ord_i = 0;
	loop(i,0,G[v].size()) {
		if(!visited[G[v][i]]) {
			dfs1(G[v][i]);
		}
	}
	order[ord_i++] = v;
}
int cc_i = 0;
void dfs2(int v){
	visited[v] = 1; 
	SCC[cc_i].pb(v);
	rSCC[v]=cc_i;
	loop(i,0,GT[v].size()) {
		if(!visited[GT[v][i]]) {
			dfs2(GT[v][i]);
		}
	}
}

void sss() {
	loop(i,0,n){
		if(!visited[i]) dfs1(i);
	}
	reverse(order, order+n);
	loop(i,0,n) visited[i] = false;
	loop(i,0,n){
		if(!visited[order[i]]){
			dfs2(order[i]);
			cc_i++;
		}
	}	
	loop(i,0,cc_i) {
		for(auto v : SCC[i]) {
			for(auto w: G[v]){
				if(rSCC[w] != i) GC[i].pb(rSCC[w]);
			}
		}
		sort(ALL(GC[i]));
		GC[i].erase(unique(ALL(GC[i])), GC[i].end());
	}
}

bool is_col(int i, int mask) {
	return (1<<i)&mask;
}
bool is_ok(int mask) {
	loop(i,0,cc_i) {
		if(is_col(i,mask)) {
			for(auto v : GC[i]) {
				if(!is_col(v,mask)) {
					return false;
				}
			}
		}
	}
	return true;
}

int main(){
	ios_base::sync_with_stdio(0);
	cin>>n;
	loop(i,0,n) {
		cin>>a[i]>>r[i];
	}
	
	loop(i,0,n) {
		loop(j,0,n) {
			if(i!=j && abs(a[i] - a[j])<=r[i]) {
				G[i].pb(j);
				GT[j].pb(i);
			}
		}
	}
	sss();
	
	/*loop(i,0,cc_i) {
		ps(i);ps(":");
		for(auto v: GC[i]) ps(v);
		entr;
	}*/
	
	int res = 0;
	loop(mask,0,(1<<cc_i)) {
		if(is_ok(mask)) res++;
	}
	pln(res);
}