1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
#include<iostream>
#include<queue>
#include<map>
#include<vector>
#include<algorithm>
#include<set>

#define N 300001
#define B 1048576
#define mp make_pair
#define fi first
#define se second

using namespace std;

long long odl[N];
long long r[N];
long long rleft[N];
long long rright[N];
int n;
long long t[B * 2 + 1];
int base;

const long long min_inf = 2 * (-1e18) - 1;
const long long max_inf = 2 * 1e18 + 1;
const long long mod = 1e9+7;

map<pair<long long, long long>, int> last_ind;
priority_queue<pair<pair<long long, long long>, long long> > q;
map<long long, int> long_to_ind;
vector<long long> vals;

void insert_left(int a) {
  long long val = rleft[a];
  a += base;
  t[a] = val;
  a >>= 1;
  while (a > 0) {
    t[a] = min(t[a << 1], t[(a << 1) + 1]);
    a >>= 1;
  }
}

long long find_left(int a, int b) {
  a += base;
  b += base;
  long long res = min(t[a], t[b]);
  while ((a >> 1) != (b >> 1)) {
    if (a % 2 == 0) {
      res = min(res, t[a + 1]);
    }
    if (b % 2 == 1) {
      res = min(res, t[b - 1]);
    }
    a >>= 1;
    b >>= 1;
  }
  return res;
}

void insert_right(int a) {
  long long val = rright[a];
  a += base;
  t[a] = val;
  a >>= 1;
  while (a > 0) {
    t[a] = max(t[a << 1], t[(a << 1) + 1]);
    a >>= 1;
  }
}

long long find_right(int a, int b) {
  a += base;
  b += base;
  long long res = max(t[a], t[b]);
  while ((a >> 1) != (b >> 1)) {
    if (a % 2 == 0) {
      res = max(res, t[a + 1]);
    }
    if (b % 2 == 1) {
      res = max(res, t[b - 1]);
    }
    a >>= 1;
    b >>= 1;
  }
  return res;
}

int find_left_in_range_index(int curr_ind) {
  long long left_range = odl[curr_ind] - r[curr_ind];
  int p = 0;
  int k = curr_ind;
  int m;
  while (p < k) {
    m = (p + k) >> 1;
    if (odl[m] < left_range) {
      p = m + 1;
    } else {
      k = m;
    }
  }
  return p;
}

int find_right_in_range_index(int curr_ind) {
  long long right_range = odl[curr_ind] + r[curr_ind];
  int p = curr_ind;
  int k = n - 1;
  int m;
  while (p < k) {
    m = ((p + k) >> 1) + (p + k) % 2;
    if (odl[m] > right_range) {
      k = m - 1;
    } else {
      p = m;
    }
  }
  return p;
}

void fill_left() {
  fill(t, t + base * 2 + 1, max_inf);
  rleft[0] = odl[0] - r[0];
  insert_left(0);

  for (int i = 1; i < n; i++) {
    int ind = find_left_in_range_index(i);
    rleft[i] = min(odl[i] - r[i], find_left(ind, i));
    insert_left(i);
  }

  bool change = true;
  while(change) {
    change = false;
    for (int i = 0; i < n; i++) {
      int ind_left = find_left_in_range_index(i);
      int ind_right = find_right_in_range_index(i);
      long long new_val = find_left(ind_left, ind_right);
      if (rleft[i] != new_val) {
        rleft[i] = new_val;
        insert_left(i);
        change = true;
      }
    }
  }
}

void fill_map_and_set_base() {
  for (int i = 0; i < n; i++) {
    vals.push_back(rleft[i]);
    vals.push_back(odl[i]);
  }
  sort(vals.begin(), vals.end());
  int ind = 0;
  long_to_ind[min_inf] = ind;
  ind++;
  long_to_ind[vals[0]] = ind;
  for (int i = 1; i < vals.size(); i++) {
    if (vals[i] != vals[i - 1]) {
      ind++;
      long_to_ind[vals[i]] = ind;
    }
  }
  vals.clear();
  for (base = 8; base <= ind; base *= 2) {}
}

void fill_right() {
  fill(t, t + base * 2 + 1, min_inf);
  rright[n - 1] = odl[n - 1] + r[n - 1];
  insert_right(n - 1);

  for (int i = n - 2; i >= 0; i--) {
    int ind = find_right_in_range_index(i);
    rright[i] = max(odl[i] + r[i], find_right(i, ind));
    insert_right(i);
  }

  bool change = true;
  while(change) {
    change = false;
    for (int i = n - 1; i >= 0; i--) {
      int ind_left = find_left_in_range_index(i);
      int ind_right = find_right_in_range_index(i);
      long long new_val = find_right(ind_left, ind_right);
      if (rright[i] != new_val) {
        rright[i] = new_val;
        insert_right(i);
        change = true;
      }
    }
  }
}

void tree_add(long long odli, long long val) {
  int a = long_to_ind[odli];
  a += base;
  while(a > 0) {
    t[a] = (t[a] + val) % mod;
    a >>= 1;
  }
}

long long sum_before(long long left_r) {
  int a = long_to_ind[left_r];
  a += base;
  long long res = 0;
  while(a > 1) {
    if (a % 2 == 1) {
      res = (t[a - 1] + res) % mod;
    }
    a >>= 1;
  }
  return res;
}

void queue_to_vec(long long right_limit) {
  while(!q.empty() && (-1) * q.top().fi.fi < right_limit) {
    int i = q.top().fi.se;
    long long res = q.top().se;
    tree_add(odl[i], res);
    q.pop();
  }
}

int main() {
  ios_base::sync_with_stdio(0);

  cin >> n;

  for (int i = 0; i < n; i++) {
    cin >> odl[i] >> r[i];
  }
  for (base = 8; base <= n; base *= 2) {}

  fill_left();
  fill_right();

  for (int i = 0; i < n; i++) {
    pair<long long, long long> x = mp(rleft[i], rright[i]);
    last_ind[x] = i;
  }

  fill_map_and_set_base();

  fill(t, t + base * 2 + 1, 0);

  tree_add(min_inf, 1);

  for (int i = 0; i < n; i++) {
    queue_to_vec(odl[i]);
    pair<long long, long long> x = mp(rleft[i], rright[i]);
    if (last_ind[x] == i) {
      q.push(mp(mp(-rright[i], i), sum_before(rleft[i])));
    }
  }
  queue_to_vec(max_inf);

  cout << t[1] << endl;

  return 0;
}