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#include <bits/stdc++.h>

using namespace std;

struct Mine
{
  int position;
  int range;
};

using Mines = vector<Mine>;

struct TestCase
{
  int mine_count;
  Mines mines;
};

TestCase read_test_case();
void solve_test_case(const TestCase&);

int main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve_test_case(read_test_case());
}

TestCase read_test_case()
{
  TestCase test_case;
  cin >> test_case.mine_count;
  test_case.mines.resize(test_case.mine_count);
  for (auto& mine : test_case.mines) cin >> mine.position >> mine.range;
  return test_case;
}

int explosion_result(const Mines&, int detonation);

void solve_test_case(const TestCase& test_case)
{
  vector<int> explosion_masks(test_case.mine_count, 0);
  for (int i = 0; i < test_case.mine_count; i++)
  {
    int max_left, max_right;
    int mask = 0;
    max_left = max_right = test_case.mines[i].position;
    for (int j = 0; j < test_case.mine_count; j++)
    {
      if (i - j > 0 && test_case.mines[i - j].position >= max_left)
      {
        mask |= (1 << (i - j));
        max_left =
            min(max_left,
                test_case.mines[i - j].position - test_case.mines[i - j].range);
        max_right =
            max(max_right,
                test_case.mines[i - j].position + test_case.mines[i - j].range);
      }

      if (i + j < test_case.mine_count &&
          test_case.mines[i + j].position <= max_right)
      {
        mask |= (1 << (i + j));
        max_left =
            min(max_left,
                test_case.mines[i + j].position - test_case.mines[i + j].range);
        max_right =
            max(max_right,
                test_case.mines[i + j].position + test_case.mines[i + j].range);
      }
    }
    explosion_masks[i] = mask;
  }

  set<int> explosions;

  for (int m = 0; m < (1 << test_case.mine_count); m++)
  {
    int e = 0;
    for (int i = 0; i < test_case.mine_count; i++)
      if (m & (1 << i)) e |= explosion_masks[i];
    explosions.insert(e);
  }

  cout << explosions.size() << "\n";
}