// #define LOCAL
#define _USE_MATH_DEFINES
#include <array>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
#include <complex>
#include <cmath>
#include <numeric>
#include <bitset>
#include <functional>
#include <random>
#include <ctime>

using namespace std;

template <typename A, typename B>
ostream& operator <<(ostream& out, const pair<A, B>& a) {
  out << "(" << a.first << "," << a.second << ")";
  return out;
}
template <typename T, size_t N>
ostream& operator <<(ostream& out, const array<T, N>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T>
ostream& operator <<(ostream& out, const vector<T>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T, class Cmp>
ostream& operator <<(ostream& out, const set<T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
  return out;
}
#ifdef LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 42
#endif
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
  cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << ": " << arg1 << " |";
  __f(comma + 1, args...);
}

typedef long long int64;
typedef pair<int, int> ii;
const int INF = 1 << 29;
const int MOD = 998244353;
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }

struct fast_ios {
  fast_ios() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
  };
} fast_ios_;

int64 power_mod(int64 a, int64 n, int p = MOD) {
  int64 ret = 1;
  for (; n; n >>= 1) {
    if (n & 1) ret = ret * a % p;
    a = a * a % p;
  }
  return ret;
}

int main() {
  int n;
  scanf("%d", &n);
  vector<int64> dp(n);
  vector<ii> a(n);
  for (int i = 0; i < n; ++i) {
    scanf("%d%d", &a[i].first, &a[i].second);
    a[i].second += a[i].first;
  }
  sort(a.begin(), a.end());
  set<ii> A;
  for (int i = n - 1; i >= 0; --i) {
    auto L = A.lower_bound({a[i].first, -1});
    auto R = A.lower_bound({a[i].second, -1});
    dp[i] = 1;
    for (auto it = L; it != R; ++it) {
      dp[i] = dp[i] * dp[it->second];
    };
    A.erase(L, R);
    dp[i] = (dp[i] + 1) % MOD;
    A.insert({a[i].first, i});
    trace(i, a[i], dp[i]);
  }
  vector<ii> C;
  for (int i = 0; i < n; ++i) {
    C.push_back({a[i].first, i});
    C.push_back({a[i].second, ~i});
  }
  sort(C.begin(), C.end());
  int cover = 0;
  int64 ret = 1;
  for (int i = 0; i < C.size(); ++i) {
    int pos = C[i].first, k = C[i].second;
  // for (auto [pos, k] : C) {
    int x = k < 0 ? -1 : 1;
    cover += x;
    if (k < 0) k = ~k;
    trace(pos, k, cover);
    if (cover == 1 && x > 0) ret = ret * dp[k] % MOD;
  }
  printf("%lld\n", ret);
  return 0;
}


Measured memory_bytes: 13044