#include <bits/stdc++.h>

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cout.tie(nullptr);
	int n, c = 0;
	std::cin >> n;
	std::vector<std::tuple<int, int, int>> vec;
	for (int i = 1; i <= n; ++i) {
		int t, d;
		std::cin >> t >> d;
		vec.emplace_back(d, t, i);
	}
	// [deadline, time, index]
	std::sort(vec.begin(), vec.end());
	int total = 1, count = 0;
	std::priority_queue<std::pair<int, int>> elements;
	for (auto [d, t, i] : vec) {
		if (total + t - 1 <= d) {
			elements.emplace(t, c);
			++count;
			total += t;
		}
		else if (!elements.empty()) {
			auto p = elements.top();
			if (p.first > t) {
				total -= p.first;
				elements.pop();
				total += t;
				elements.emplace(t, c);
			}
		}
		++c;
	}
	std::cout << count << '\n';
	std::vector<int> pl;
	while (!elements.empty()) {
		auto [t, i] = elements.top();
		elements.pop();
		pl.push_back(i);
	}
	std::sort(pl.begin(), pl.end());
	int cur = 1;
	for (auto j : pl) {
		auto [d, t, i] = vec[j];
		std::cout << i << " " << cur << '\n';
		cur += t;
	}
}