CF 545C

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 1e5 + 131;
struct Tree
{
    int pos, val;
    int MaxPos;
}T[maxn];
int Dp[maxn];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    memset(Dp,0,sizeof(Dp));
    for(int i = 1; i <= n; ++i)
    {
        cin >> T[i].pos >> T[i].val;
        T[i].MaxPos = T[i].pos;
    }
    Dp[1] =1;
    if(n == 1) cout << 1 <<endl;
    else if(n == 2) cout <<2 << endl;
    else
    {
        for(int i = 2; i < n; ++i)
        {
            int P = T[i].pos, H = T[i].val;
            int pre = T[i-1].MaxPos;
            int l = Dp[i-1] , r = Dp[i-1];
            if(P + H < T[i+1].pos)  r++ , T[i].MaxPos = P+H;
            if(P - H > pre)         l++ , T[i].MaxPos = P;
            Dp[i] = max(Dp[i-1], max(l, r) );
        }
        Dp[n] = Dp[n-1] + 1;
        cout << Dp[n] << endl;
    }
}