using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;

public static class P
{
    public static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        var robots = Enumerable.Range(0, n).Select(x => Console.ReadLine().Split().Select(int.Parse).ToArray()).OrderBy(x => x[0]).ToArray();
        int[] chainUntil = new int[n];
        Func<int, ModInt> solve = null;
        solve = x =>
        {
            ModInt res = 1;
            int next = x + 1;
            var max = robots[x].Sum();
            while (next < n && robots[next][0] < max)
            {
                res *= solve(next);
                next = chainUntil[next] + 1;
            }
            chainUntil[x] = next - 1;
            res += 1;
            return res;
        };
        ModInt allRes = 1;
        var i = 0;
        while (i < n)
        {
            allRes *= solve(i);
            i = chainUntil[i] + 1;
        }
        Console.WriteLine(allRes);
    }
}


class UnionFind
{
    public int Size { get; private set; }
    public int GroupCount { get; private set; }
    public IEnumerable<int> AllRepresents => Parent.Where((x, y) => x == y);
    int[] Sizes;
    int[] Parent;
    public UnionFind(int count)
    {
        Size = count;
        GroupCount = count;
        Parent = new int[count];
        Sizes = new int[count];
        for (int i = 0; i < count; i++) Sizes[Parent[i] = i] = 1;
    }
    public bool TryUnite(int x, int y)
    {
        int xp = Find(x);
        int yp = Find(y);
        if (yp == xp) return false;
        if (Sizes[xp] < Sizes[yp]) { var tmp = xp; xp = yp; yp = tmp; }
        GroupCount--;
        Parent[yp] = xp;
        Sizes[xp] += Sizes[yp];
        return true;
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int GetSize(int x) => Sizes[Find(x)];
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int Find(int x)
    {
        while (x != Parent[x]) x = (Parent[x] = Parent[Parent[x]]);
        return x;
    }
}



struct ModInt
{
    public const int Mod = 998244353;
    const long POSITIVIZER = ((long)Mod) << 31;
    long Data;
    public ModInt(long data) { if ((Data = data % Mod) < 0) Data += Mod; }
    public static implicit operator long(ModInt modInt) => modInt.Data;
    public static implicit operator ModInt(long val) => new ModInt(val);
    public static ModInt operator +(ModInt a, int b) => new ModInt() { Data = (a.Data + b + POSITIVIZER) % Mod };
    public static ModInt operator +(ModInt a, long b) => new ModInt(a.Data + b);
    public static ModInt operator +(ModInt a, ModInt b) { long res = a.Data + b.Data; return new ModInt() { Data = res >= Mod ? res - Mod : res }; }
    public static ModInt operator -(ModInt a, int b) => new ModInt() { Data = (a.Data - b + POSITIVIZER) % Mod };
    public static ModInt operator -(ModInt a, long b) => new ModInt(a.Data - b);
    public static ModInt operator -(ModInt a, ModInt b) { long res = a.Data - b.Data; return new ModInt() { Data = res < 0 ? res + Mod : res }; }
    public static ModInt operator *(ModInt a, int b) => new ModInt(a.Data * b);
    public static ModInt operator *(ModInt a, long b) => a * new ModInt(b);
    public static ModInt operator *(ModInt a, ModInt b) => new ModInt() { Data = a.Data * b.Data % Mod };
    public static ModInt operator /(ModInt a, ModInt b) => new ModInt() { Data = a.Data * GetInverse(b) % Mod };
    public static bool operator ==(ModInt a, ModInt b) => a.Data == b.Data;
    public static bool operator !=(ModInt a, ModInt b) => a.Data != b.Data;
    public override string ToString() => Data.ToString();
    public override bool Equals(object obj) => (ModInt)obj == this;
    public override int GetHashCode() => (int)Data;
    static long GetInverse(long a)
    {
        long div, p = Mod, x1 = 1, y1 = 0, x2 = 0, y2 = 1;
        while (true)
        {
            if (p == 1) return x2 + Mod; div = a / p; x1 -= x2 * div; y1 -= y2 * div; a %= p;
            if (a == 1) return x1 + Mod; div = p / a; x2 -= x1 * div; y2 -= y1 * div; p %= a;
        }
    }
}

Measured memory_bytes: 68260