#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <memory.h>

#define ABS(a) ((a>0)?a:-(a))
#define MIN(a,b) ((a<b)?(a):(b))
#define MAX(a,b) ((a<b)?(b):(a))
#define FOR(i,a,n) for (int i=(a);i<(n);++i)
#define FI(i,n) for (int i=0; i<(n); ++i)
#define pnt pair <int, int>
#define mp make_pair
#define PI 3.14159265358979
#define MEMS(a,b) memset(a,b,sizeof(a))
#define LL long long
#define U unsigned
using namespace std;

vector<pnt > a;
int dp[1010][2];
LL T;

int r(int p, int v)
{
    if (p == a.size())
        return 0;
    if (dp[p][v] != -1)
        return dp[p][v];
    int res = a.size();
    if (v == 0)
    {
        FOR(i, p, a.size())
        {
            if (a[i].first - a[p].first <= T + T)
            {
                res = min(res, 1 + r(i + 1, v));
                res = min(res, 1 + r(i + 1, v ^ 1));
            }
            else
                break;
        }
    }
    else
    {
        LL rt = (LL)a[p].first - T - 1;
        FOR(i, p, a.size())
        {
            LL le = MAX(a[i].first - T, rt + 1);
            LL ri = a[i].first + T;
            if (ri-le + 1 < a[i].second)
                break;
            rt = le + a[i].second - 1;
            res = min(res, r(i + 1, v ^ 1));
            //res = min(res, r(i + 1, v));
        }
    }
    return dp[p][v] = res;
}
class CatsOnTheLineDiv1 {
public:
    int getNumber(vector <int> position, vector <int> count, int t) {
        int res = 0;
        a.clear();
        FOR(i, 0, position.size())
            a.push_back(mp(position[i], count[i]));
        int n = a.size();
        sort(a.begin(), a.end());
        MEMS(dp, -1);
        T = t;
        res = min(r(0, 0), r(0, 1));
        return res;
    }

};