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//#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
//~ while (clock()<=69*CLOCKS_PER_SEC)

#define ll long long
#define ld long double
#define pi pair<int,int>
#define pd pair<ld,ld>
#define ft first
#define sd second
#define pb push_back
#define eb emplace_back
#define FOR(i,a,b) for(int i=(a); i<=(b);i++)
#define F(i,a,b) FOR(i,(a),(b)-1)
#define REV(i,a,b) for(int i=(a); i>=(b);i--)
#define VI vector<int>
#define VPI vector<pi>
#define VPD vector<pd>
#define PI 3.14159265
#define all(x) (x).begin(), (x).end()
#define sz(a) (int)((a).size())
#define int long long

template<class TH> void _dbg(const char *sdbg, TH h){cerr<<sdbg<<"="<<h<<"\n";}
template<class TH, class... TA> void _dbg(const char *sdbg, TH h, TA... a) {
    while(*sdbg!=',')cerr<<*sdbg++;cerr<<"="<<h<<","; _dbg(sdbg+1, a...);
}
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const long long K = 1000;
const long long KK = K*K;
const long long MIL = KK*K;
const long long INF = MIL*MIL;
const long long MOD = 1e9 + 7;
const long long N = 30, M=310;

bool mac[N][N];

void solve() {
    int n;
    cin >> n;
    VPI V(n);
    F(i, 0, n) {
        cin >> V[i].ft >> V[i].sd;
    }

    F(i, 0, n) {
        F(j, 0, n) {
            if (i == j)
                continue;
            if (abs(V[i].ft - V[j].ft) <= V[i].sd) {
                mac[i][j] = true;
            }
        }
    }
    
    int res = 0;
    map<int, bool> mapa;
    F(i, 0, 1 << n) {
        bitset<20> bits = i;
        bool zmiana = true;
        while (zmiana) {
            zmiana = false;
            F(j, 0, n) {
                if (bits[j]) {
                    F(k, 0, n) {
                        if (mac[j][k] && bits[k] == 0) {
                            bits[k] = 1;
                            zmiana = true;
                        }
                    }
                }
            }
        }
        if (!mapa[bits.to_ulong()]) {
            res++;
            mapa[bits.to_ulong()] = true;
        }
    }
    
    cout << res << "\n";


}

int32_t main() {
//	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);

    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    cout.tie(0);
    cerr.tie(0);
    cout << setprecision(9) << fixed;
    cerr << setprecision(6) << fixed;
    int test = 1, f;
//    cin >> test;
    F(_test, 0, test) {
        //cout<<"Case #"<<_test + 1<<": ";
        solve();
//		if(_test == 1)
//            return 0;
    }
}
/*
4
3 4 5 -5

 */