#include<bits/stdc++.h>

using std::cin;
using std::cout;
using ll = long long;
using i128 = __int128;

const int N = 200005;

int n, c;
struct pr { int val; ll cnt; };
int t[N], d[N];
ll st;
std::vector<pr> v;
int check(ll T) {
	v.clear();
	i128 mx = 0;
	for(int i = 1;i <= n;++i) {
		int turn = t[i] / d[i];
		if(turn >= T) {
			v.push_back({d[i], T});
			++mx;
		} else {
			v.push_back({d[i], turn});
			if(t[i] % d[i]) {
				if (turn == T - 1) ++mx; 
				v.push_back({t[i] % d[i], 1});
			}
		}
	}
	sort(v.begin(), v.end(), [](auto x, auto y) {
		return x.val > y.val;
	});
	i128 ccc = 0;
	for (auto vv : v) ccc += vv.cnt;
	mx = std::max<i128>(ccc - i128(T-1) * c, mx);
	i128 cnt = (i128) T * c;
	ll sum = 0;
	for(auto x : v) {
		ll sub = std::min<i128>(cnt, x.cnt);
		sum += x.val * sub;
		cnt -= sub;
	}
	return st - sum <= c - mx;
}
int main() {
	cin >> n >> c;
	for(int i = 1;i <= n;++i) {
		cin >> t[i] >> d[i];
		st += t[i];
	}
	ll l = 0, r = 1e18 + 1;
	for(;l + 1 < r;) {
		ll mid = (l + r) >> 1;
		if(check(mid)) {
			r = mid;
		} else {
			l = mid;
		}
	}
	cout << r - 1 << '\n';
}