Problem:
Score : 600 points

Problem Statement

There are N robots numbered 1 to N placed on a number line. Robot i is placed at coordinate X_i. When activated, it will travel the distance of D_i in the positive direction, and then it will be removed from the number line. All the robots move at the same speed, and their sizes are ignorable.

Takahashi, who is a mischievous boy, can do the following operation any number of times (possibly zero) as long as there is a robot remaining on the number line.

Choose a robot and activate it. This operation cannot be done when there is a robot moving.

While Robot i is moving, if it touches another robot j that is remaining in the range [X_i, X_i + D_i) on the number line, Robot j also gets activated and starts moving. This process is repeated recursively.

How many possible sets of robots remaining on the number line are there after Takahashi does the operation some number of times? Compute this count modulo 998244353, since it can be enormous.

Constraints

1 \leq N \leq 2 \times 10^5

-10^9 \leq X_i \leq 10^9

1 \leq D_i \leq 10^9

X_i \neq X_j (i \neq j)

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
X_1 D_1
:
X_N D_N

Output

Print the number of possible sets of robots remaining on the number line, modulo 998244353.

Sample Input 1

2
1 5
3 3

Sample Output 1

3

There are three possible sets of robots remaining on the number line: \{1, 2\}, \{1\}, and \{\}.

These can be achieved as follows:

If Takahashi activates nothing, the robots \{1, 2\} will remain.

If Takahashi activates Robot 1, it will activate Robot 2 while moving, after which there will be no robots on the number line. This state can also be reached by activating Robot 2 and then Robot 1.

If Takahashi activates Robot 2 and finishes doing the operation, the robot \{1\} will remain.

Sample Input 2

3
6 5
-1 10
3 3

Sample Output 2

5

There are five possible sets of robots remaining on the number line: \{1, 2, 3\}, \{1, 2\}, \{2\}, \{2, 3\}, and \{\}.

Sample Input 3

4
7 10
-10 3
4 3
-4 3

Sample Output 3

16

None of the robots influences others.

Sample Input 4

20
-8 1
26 4
0 5
9 1
19 4
22 20
28 27
11 8
-3 20
-25 17
10 4
-18 27
24 28
-11 19
2 27
-2 18
-1 12
-24 29
31 29
29 7

Sample Output 4

110

Remember to print the count modulo 998244353.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

/**
 * @author derrick20
 */
import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        FastScanner sc = new FastScanner();
        PrintWriter out = new PrintWriter(System.out);

        int N = sc.nextInt();
        Segment[] segs = new Segment[N];
        for (int i = 0; i < N; i++) {
            int l = sc.nextInt();
            int d = sc.nextInt();
            segs[i] = new Segment(l, l + d);
        }

        Arrays.sort(segs);
        TreeMap<Integer, Integer> leftToIdx = new TreeMap<>();
        for (int i = 0; i < N; i++) {
            // all unique!
            leftToIdx.put(segs[i].l, i);
        }
        leftToIdx.put(Integer.MAX_VALUE, N);

        int[] init = new int[N + 1];
        SegmentTree st = new SegmentTree(init);
        long[] suffix = new long[N + 1];
        suffix[N] = 1;
        // st stores the farthest right idx something at a given
        // spot can reach
//        System.out.println(Arrays.toString(segs));
        for (int i = N - 1; i >= 0; i--) {
            Segment seg = segs[i];
            // of course, if we are the rightmost thing, then all we
            // can reach is our own idx
            int idx = leftToIdx.get(seg.l);
            st.update(idx, idx);
            int farthestIdx = (int) st.queryRange(idx, leftToIdx.lowerEntry(seg.r).getValue());
            st.update(idx, farthestIdx);
            long aboveWays = suffix[farthestIdx + 1];
            suffix[i] = (suffix[i + 1] + aboveWays) % mod;

        }
//        System.out.println(Arrays.toString(suffix));
        out.println(suffix[0]);
        out.close();
    }

    static long mod = 998244353;

    static class Segment implements Comparable<Segment> {
        int l, r;
        public Segment(int ll, int rr) {
            l = ll; r = rr;
        }
        public String toString() {
            return "[" + l + ", " + r + ")";
        }
        public int compareTo(Segment s2) {
            return l - s2.l != 0 ? l - s2.l : r - s2.r;
        }
    }

    static class BIT {
        long[] tree;
        public BIT(int max) {
            tree = new long[max + 1];
        }

        public long sum(int i) {
            long ans = 0;
            for (; i > 0; i -= i & -i) {
                ans += tree[i];
                ans %= mod;
            }
            return ans;
        }

        public void add(int i, long val) {
            for (; i < tree.length; i += i & -i) {
                tree[i] += val;
                tree[i] %= mod;
            }
        }
    }

    static class SegmentTree {
        int[] arr;
        long[] tree;
        int[] lo, hi;
        int N;
        // a value that doesn't affect an output (for min it's infinity)
        long NEUTRAL = 0;
        private long merge(long leftVal, long rightVal) {
            return Math.max(leftVal, rightVal);
        }

        public SegmentTree(int[] arr) {
            this.arr = arr;
            N = arr.length;
            tree = new long[4 * N + 1];
            lo = new int[4 * N + 1];
            hi = new int[4 * N + 1];
            // The original bounds of responsibility the root will be [0, N-1]
            constructSegmentTree(1, 0, N - 1);
        }

        public String toString() {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < N; i++) {
                sb.append(queryRange(i, i) + " ");
            }
            return sb.toString();
        }

        // Construct a node which is responsible for the range specified: left to right inclusive!
        private void constructSegmentTree(int node, int left, int right) {
            if (left == right) {
                lo[node] = left;
                hi[node] = right;
                tree[node] = arr[left];
            } else {
                lo[node] = left;
                hi[node] = right;
                int mid = (left + right) / 2;
                constructSegmentTree(leftChild(node), left, mid);
                constructSegmentTree(rightChild(node), mid + 1, right);
                tree[node] = merge(tree[leftChild(node)], tree[rightChild(node)]);
            }
        }

        public long queryRange(int leftBound, int rightBound) {
            return queryRangeHelper(1, leftBound, rightBound);
        }

        // Query from a fixed range left, right
        private long queryRangeHelper(int node, int leftBound, int rightBound) {
            if (hi[node] < leftBound || rightBound < lo[node]) {
                // We are either too far left or too far right
                return NEUTRAL;
            } else if (leftBound <= lo[node] && hi[node] <= rightBound) {
                // Perfectly contained!
                return tree[node];
            } else {
                // Partial covering
                long leftVal = queryRangeHelper(leftChild(node), leftBound, rightBound);
                long rightVal = queryRangeHelper(rightChild(node), leftBound, rightBound);
                long ans = merge(leftVal, rightVal);
                return ans;
            }
        }

        public void update(int index, int val) {
            updateHelper(1, index, val);
        }

        private void updateHelper(int node, int index, int val) {
            if (hi[node] < index || index < lo[node]) {
                // We are either too far left or too far right
                return;
            } else if (index == lo[node] && hi[node] == index) {
                // Found it!
                tree[node] = val;
            } else {
                // Not there yet!
                updateHelper(leftChild(node), index, val);
                updateHelper(rightChild(node), index, val);
                // Make sure to fix our values on the way back up!
                tree[node] = merge(tree[leftChild(node)], tree[rightChild(node)]);
            }
        }

        private int leftChild(int node) {
            return 2 * node;
        }

        private int rightChild(int node) {
            return 2 * node + 1;
        }
    }

    static class FastScanner {
        private int BS = 1<<16;
        private char NC = (char)0;
        private byte[] buf = new byte[BS];
        private int bId = 0, size = 0;
        private char c = NC;
        private double cnt = 1;
        private BufferedInputStream in;

        public FastScanner() {
            in = new BufferedInputStream(System.in, BS);
        }

        public FastScanner(String s) {
            try {
                in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
            }
            catch (Exception e) {
                in = new BufferedInputStream(System.in, BS);
            }
        }

        private char getChar(){
            while(bId==size) {
                try {
                    size = in.read(buf);
                }catch(Exception e) {
                    return NC;
                }
                if(size==-1)return NC;
                bId=0;
            }
            return (char)buf[bId++];
        }

        public int nextInt() {
            return (int)nextLong();
        }

        public int[] nextInts(int N) {
            int[] res = new int[N];
            for (int i = 0; i < N; i++) {
                res[i] = (int) nextLong();
            }
            return res;
        }

        public long[] nextLongs(int N) {
            long[] res = new long[N];
            for (int i = 0; i < N; i++) {
                res[i] = nextLong();
            }
            return res;
        }

        public long nextLong() {
            cnt=1;
            boolean neg = false;
            if(c==NC)c=getChar();
            for(;(c<'0' || c>'9'); c = getChar()) {
                if(c=='-')neg=true;
            }
            long res = 0;
            for(; c>='0' && c <='9'; c=getChar()) {
                res = (res<<3)+(res<<1)+c-'0';
                cnt*=10;
            }
            return neg?-res:res;
        }

        public double nextDouble() {
            double cur = nextLong();
            return c!='.' ? cur:cur+nextLong()/cnt;
        }

        public String next() {
            StringBuilder res = new StringBuilder();
            while(c<=32)c=getChar();
            while(c>32) {
                res.append(c);
                c=getChar();
            }
            return res.toString();
        }

        public String nextLine() {
            StringBuilder res = new StringBuilder();
            while(c<=32)c=getChar();
            while(c!='\n') {
                res.append(c);
                c=getChar();
            }
            return res.toString();
        }

        public boolean hasNext() {
            if(c>32)return true;
            while(true) {
                c=getChar();
                if(c==NC)return false;
                else if(c>32)return true;
            }
        }
    }
}