RT，用的是线段树优化建图 + Tarjan + 记忆化搜索版的 DAGdp，目前 WA $37 \operatorname{pts}$（校内 OJ WA + RE $30 \operatorname{pts}$）/kk

代码：

#include <iostream>
#include <algorithm>
#include <stack>
#include <cstdio>

using namespace std;

typedef long long ll;

typedef struct {
	int l;
	int r;
} Node;

typedef struct {
	int nxt;
	int end;
} Edge;

const int mod = 1e9 + 7;
int cnt = 0;
int leaf[500007], pos[2000007], l[500007], R[500007], head[2000007], dfn[2000007], low[2000007], belong[2000007], LL[2000007], rr[2000007];
ll x[500007], r[500007];
bool vis1[2000007], vis2[2000007], vis3[2000007], vis4[2000007];
Edge edge[9500007];
Node tree[2000007];
stack<int> s;

inline void init(int n){
	cnt = 0;
	for (register int i = 1; i <= n; i++){
		head[i] = 0;
	}
}

inline int read_int(){
	int ans = 0;
	char ch = getchar();
	while (ch < '0' || ch > '9'){
		ch = getchar();
	}
	while (ch >= '0' && ch <= '9'){
		ans = ans * 10 + (ch ^ 48);
		ch = getchar();
	}
	return ans;
}

inline ll read_ll(){
	ll ans = 0;
	char ch = getchar();
	while (ch < '0' || ch > '9'){
		ch = getchar();
	}
	while (ch >= '0' && ch <= '9'){
		ans = ans * 10 + (ch ^ 48);
		ch = getchar();
	}
	return ans;
}

inline void add_edge(int start, int end){
	cnt++;
	edge[cnt].nxt = head[start];
	head[start] = cnt;
	edge[cnt].end = end;
}

void build(int x, int l, int r){
	tree[x].l = l;
	tree[x].r = r;
	if (l == r){
		leaf[l] = x;
		pos[x] = l;
		return;
	}
	int ls = x * 2, rs = x * 2 + 1, mid = (l + r) >> 1;
	add_edge(x, ls);
	add_edge(x, rs);
	build(ls, l, mid);
	build(rs, mid + 1, r);
}

void connect1(int x, int u, int l, int r){
	if (l <= tree[x].l && tree[x].r <= r){
		add_edge(leaf[u], x);
		return;
	}
	int mid = (tree[x].l + tree[x].r) >> 1;
	if (l <= mid) connect1(x * 2, u, l, r);
	if (r > mid) connect1(x * 2 + 1, u, l, r);
}

void tarjan(int u, int &id, int &scc_cnt){
	dfn[u] = low[u] = ++id;
	vis1[u] = vis2[u] = true;
	s.push(u);
	for (register int i = head[u]; i != 0; i = edge[i].nxt){
		int x = edge[i].end;
		if (!vis1[x]){
			tarjan(x, id, scc_cnt);
			low[u] = min(low[u], low[x]);
		} else if (vis2[x]){
			low[u] = min(low[u], dfn[x]);
		}
	}
	if (dfn[u] == low[u]){
		int cur;
		LL[++scc_cnt] = 0x7fffffff;
		do {
			cur = s.top();
			s.pop();
			belong[cur] = scc_cnt;
			vis2[cur] = false;
			if (pos[cur] != 0){
				LL[scc_cnt] = min(LL[scc_cnt], l[pos[cur]]);
				rr[scc_cnt] = max(rr[scc_cnt], R[pos[cur]]);
			}
		} while (cur != u);
	}
}

void connect2(int x, int u, int l, int r){
	if (l <= tree[x].l && tree[x].r <= r){
		if (belong[leaf[u]] != belong[x]) add_edge(belong[leaf[u]], belong[x]);
		return;
	}
	int mid = (tree[x].l + tree[x].r) >> 1;
	if (l <= mid) connect2(x * 2, u, l, r);
	if (r > mid) connect2(x * 2 + 1, u, l, r);
}

void dfs(int u){
	if (vis3[u]) return;
	for (register int i = head[u]; i != 0; i = edge[i].nxt){
		int x = edge[i].end;
		dfs(x);
		LL[u] = min(LL[u], LL[x]);
		rr[u] = max(rr[u], rr[x]);
	}
	vis3[u] = true;
}

int main(){
	int n = read_int(), m = n * 4, id = 0, scc_cnt = 0;
	ll ans = 0;
	build(1, 1, n);
	for (register int i = 1; i <= n; i++){
		x[i] = read_ll();
		r[i] = read_ll();
	}
	for (register int i = 1; i <= n; i++){
		l[i] = lower_bound(x + 1, x + n + 1, x[i] - r[i]) - x;
		R[i] = upper_bound(x + 1, x + n + 1, x[i] + r[i]) - x - 1;
		connect1(1, i, l[i], R[i]);
	}
	for (register int i = 1; i <= m; i++){
		if (!vis1[i]) tarjan(i, id, scc_cnt);
	}
	init(scc_cnt);
	for (register int i = 1; i <= n; i++){
		connect2(1, i, l[i], R[i]);
	}
	for (register int i = 1; i <= n; i++){
		int pos = belong[leaf[i]];
		dfs(pos);
		ans = (ans + (ll)i * (rr[pos] - LL[pos] + 1) % mod) % mod;
	}
	cout << ans;
	return 0;
}