codeforces 545C（贪心）

#include<bits/stdc++.h>
#define x first
#define y second
#define PB push_back
#define mst(x,a) memset(x,a,sizeof(x))
#define all(a) begin(a),end(a)
#define rep(x,l,u) for(ll x=l;x<u;x++)
#define rrep(x,l,u) for(ll x=l;x>=u;x--)
#define IOS ios::sync_with_stdio(false);cin.tie(0);
using namespace std;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef pair<long,long> PLL;
typedef pair<char,char> PCC;
typedef long long ll;
const int N=1e5+10;
const int M=1e6+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;
struct node{
    ll pos,h;
}Node[N];
ll used[N];
void solve(){
    int n;cin>>n;
    rep(i,1,n+1) cin>>Node[i].pos>>Node[i].h;
    int ans=0;
    rep(i,0,n+2) used[i]=1e18;
    used[0]=-1e18;
    Node[0].pos=-1e18;//第一棵树向左砍
    Node[n+1].pos=1e18;//最后一颗树向右砍
    rep(i,1,n+1){
        ll left=Node[i].pos-Node[i].h;
        ll right=Node[i].pos+Node[i].h;
        if(left>Node[i-1].pos && left>used[i-1]){
            ans++;
            used[i]=left;
        }else if(right<Node[i+1].pos && right<used[i+1]){
            ans++;
            used[i]=right;
        }else{
            used[i]=-1e18;
        }
    }
    cout<<ans<<endl;
}
int main(){
    IOS;
    solve();
    return 0;
}