#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}());
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=201000;
int t[N],d[N],n,c,cnt[N];
vector<array<int,3>> ev;

bool check(ll md) {
	ll tots=0;
	rep(i,0,n) {
		cnt[i]=0;
		tots+=t[i];
	}
	ll cc=0;
	for (auto [d,t,id]:ev) {
		ll mt=min((ll)t,md-cnt[id]);
		cnt[id]+=mt;
		cc+=mt;
		tots-=d*mt;
	}
	int last=0;
	rep(i,0,n) if (cnt[i]==md) {
		last++;
	}
	cc=max(cc-(__int128_t)(md-1)*c,(__int128_t)0);
	return tots<=c-cc;
}

int main() {
	scanf("%d%d",&n,&c);
	ll l=0,r=0;
	rep(i,0,n) {
		scanf("%d%d",t+i,d+i);
		r+=(t[i]+d[i]-1)/d[i];
	}
	rep(i,0,n) {
		ev.pb({d[i],t[i]/d[i],i});
		if (t[i]%d[i]) ev.pb({t[i]%d[i],1,i});
	}
	while (l+1<r) {
		ll md=(l+r)/2;
		if (check(md)) r=md; else l=md;
	}
	printf("%lld\n",l);
}