#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;

// chmax, chmin
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return 1;
  }
  return 0;
}

template <typename T>
function<T(T, T)> op_max = [](T a, T b) -> T { return max(a, b); };
template <typename T>
function<T(T, T)> op_min = [](T a, T b) -> T { return min(a, b); };

template <typename T>
function<T(T, T)> op_sum = [](T a, T b) -> T { return a + b; };

namespace detail
{
  template <typename T, std::size_t NDIMS>
  struct vector_builder
  {
    using type = std::vector<typename vector_builder<T, NDIMS - 1>::type>;

    static type make(std::vector<std::size_t> dims, const T &v = {})
    {
      const auto vec = std::vector<T>(dims.empty() ? 0 : dims.back(), v);
      if (!dims.empty())
        dims.pop_back();
      return vector_builder<std::vector<T>, NDIMS - 1>::make(dims, vec);
    }
  };

  template <typename T>
  struct vector_builder<T, 1>
  {
    using type = std::vector<T>;

    static type make(std::vector<std::size_t> dims, const T &v = {})
    {
      return type(dims.empty() ? 0 : dims.back(), v);
    }
  };
} // namespace detail

template <typename T, typename... SIZE_T>
auto exvector(const T &v, SIZE_T... dims)
{
  static_assert(sizeof...(dims) != 0, "invalid dimension");
  std::vector<std::size_t> vec_dims{dims...};
  return detail::vector_builder<T, sizeof...(dims)>::make(vec_dims, v);
}

using namespace std;
//********************  dumps ************************//

template <typename T>
void dump(const T &data, vector<int> &iter)
{
  cout << data << " ";
}
template <typename T>
void dump(const vector<T> &data, vector<int> &iter)
{
  for (auto elem : data)
    dump(elem, iter);
  cout << endl;
}

template <typename T>
void dump(const vector<vector<T>> &data, vector<int> &iter)
{
  for (auto elem : iter)
  {
    cout << "[" << elem << "]";
  }
  cout << endl;
  for (int i = 0; i < data.size(); i++)
  {
    iter.push_back(i);
    dump(data[i], iter);
    iter.pop_back();
  }
  cout << endl;
}

template <typename T>
void dump(const vector<T> &data, int dummy)
{
  for (int i = 0; i < data.size(); i++)
  {
    cout << "[" << i << "] " << data[i] << endl;
  }
}
template <typename T>
void dump(const T &data)
{ // T : data, U = base type val.
  vector<int> iter;
  dump(data, iter);
}
///////////////////////////////////////////////

const long long MOD = 998244353;

const long long MOD_CONST = 998244353;
long long mul_mod(long long a, long long b, const long long MOD)
{
  return b ? (mul_mod(a * 2, b / 2, MOD) + (b & 1 ? a : 0)) % MOD : 0;
}

long long bpow_mod(long long a, long long b, const long long MOD)
{
  return (b ? bpow_mod(a * a % MOD, b / 2, MOD) * (b & 1 ? a : 1) : 1) % MOD;
}

long long inv_mod(long long a, const long long MOD)
{
  return bpow_mod(a, MOD - 2, MOD);
}
template <long long param = MOD_CONST, bool fast = false>
class mint
{
private:
  using Z = int;
  using N = unsigned int;
  using ZZ = long long;
  using NN = unsigned long long;
  struct
  {
  } constexpr static exact{};
  // Using Z deliberately to avoid Z -> N promotion.
  template <class Ret = ZZ &>
  static auto modulo() -> std::enable_if_t<(param <= 0), Ret>
  {
    static ZZ mod = 0;
    return mod;
  }
  template <class Ret = const ZZ>
  static auto mod() -> std::enable_if_t<(param <= 0), Ret>
  {
    return modulo();
  }
  template <class Ret = const ZZ>
  static constexpr auto mod() -> std::enable_if_t<(param > 0), Ret>
  {
    return param;
  }

public:
  template <class Arg = ZZ>
  static void set_modulo(const std::enable_if_t<(param <= 0), Arg> mod)
  {
    modulo() = mod;
  }
  long long v;

  constexpr mint() : v(0) {}

  constexpr mint(long long v)
      : v(fast ? (v)
               : (v < 0 ? (v % mod() + mod()) % mod()
                        : (v >= mod() ? v % mod() : v))) {}
  constexpr long long get_mod() { return mod(); }
  long long get_val() { return v; }
  void take_mod() { v %= mod(); }
};
template <long long param, bool fast>
ostream &operator<<(ostream &os, mint<param, fast> &x)
{
  return os << (x.v % x.get_mod() + x.get_mod()) % x.get_mod();
}

template <long long param, bool fast, bool fast2>
bool operator==(mint<param, fast> &a, mint<param, fast2> b)
{
  return a.v == b.v;
}
template <long long param, bool fast, bool fast2>
mint<param, fast> &operator+=(mint<param, fast> &a, mint<param, fast2> b)
{
  return a = a.v + b.v;
}
template <long long param>
mint<param> &operator-=(mint<param> &a, mint<param> b)
{
  return a = a.v - b.v;
}
template <long long param>
mint<param> &operator*=(mint<param> &a, mint<param> b)
{
  return a = a.v * b.v;
}
template <long long param>
mint<param> &operator/=(mint<param> &a, mint<param> b)
{
  return a = a.v * inv_mod(b.v, a.get_mod());
}
template <long long param, bool fast, bool fast2>
mint<param, fast> operator+(mint<param, fast> a, mint<param, fast2> b)
{
  return a += b;
}
template <long long param>
mint<param> operator-(mint<param> a, mint<param> b)
{
  return a -= b;
}
template <long long param>
mint<param> operator*(mint<param> a, mint<param> b)
{
  return a *= b;
}
template <long long param>
mint<param> operator/(mint<param> a, mint<param> b)
{
  return a /= b;
}
template <long long param, bool fast>
mint<param, fast> &operator+=(mint<param, fast> &a, long long b)
{
  return a = a.v + b;
}
template <long long param>
mint<param> &operator-=(mint<param> &a, long long b)
{
  return a = a.v - b;
}
template <long long param>
mint<param> &operator*=(mint<param> &a, long long b)
{
  return a = a.v * b;
}
template <long long param>
mint<param> &operator/=(mint<param> &a, long long b)
{
  return a = a.v * inv_mod(b, a.get_mod());
}
template <long long param, bool fast>
mint<param, fast> operator+(mint<param> a, long long b)
{
  return a += b;
}
template <long long param>
mint<param> operator-(mint<param> a, long long b)
{
  return a -= b;
}
template <long long param>
mint<param> operator*(mint<param> a, long long b)
{
  return a *= b;
}
template <long long param>
mint<param> operator/(mint<param> a, long long b)
{
  return a /= b;
}

void solve(long long N, std::vector<long long> X, std::vector<long long> D)
{
  vector<PII> data;
  for (int i = 0; i < N; i++)
    data.push_back(PII(X[i], D[i]));
  sort(data.begin(), data.end());

  mint<> ans = 1;
  mint<> cnt = 0;
  //priority_queue<PII, vector<PII>, greater<PII>> sta;
  stack<PII> sta;
  for (auto xd : data)
  {
    LL x = xd.first;
    LL d = xd.second;

    while (!sta.empty())
    {
      LL y = x + d;
      auto val = sta.top();
      if (x >= val.first)
      {
        // /cout << x << " " << val.second << endl;
        ans += val.second;
        sta.pop();
      }
      else
      {
        break;
      }
    }
    sta.push(PII(x + d, ans.get_val()));
  }
  while (!sta.empty())
  {
    //cout << sta.top().second << endl;
    ans += sta.top().second;
    sta.pop();
  }
  cout << ans << endl;
}

int main()
{
  cout << setprecision(10);
  long long N;
  scanf("%lld", &N);
  std::vector<long long> X(N);
  std::vector<long long> D(N);
  for (int i = 0; i < N; i++)
  {
    scanf("%lld", &X[i]);
    scanf("%lld", &D[i]);
  }
  solve(N, std::move(X), std::move(D));
  return 0;
}


Measured memory_bytes: 9836