#include<bits/stdc++.h>

using namespace std;

typedef pair<int, int> pi;
typedef double db;
typedef vector<db> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef vector<vvvd> vvvvd;
typedef long long ll;
typedef array<int, 3> ai;

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) FOR(i, 0, a)
#define mp make_pair
#define rsz resize
#define pb push_back
#define F first 
#define S second 

int n, c, pre;
ll cur, sub, l, r, ans;
vector<bool> fin;
vector<int> t, d, cnt;
vector<ai> events;
set<pi> s;

ll dec(ll tm) {
    fill(fin.begin(), fin.end(), false);
    fill(cnt.begin(), cnt.end(), 0);
    ll dec = 0, spots = tm * c;
    for (ai e : events) {
        if (e[2] >= n && !fin[e[2]-n]) continue;
        ll take = min({tm - cnt[e[2]%n], spots, (ll)e[1]});
        dec += e[0] * take;
        spots -= take;
        cnt[e[2]%n] += take;
        if (e[2] < n && take == e[1]) fin[e[2]] = true;
    }
    return dec;
}
bool check(ll tm) {
    if (cur-dec(tm) <= c) return true;
    return false;
}

int main() {
    cin.tie(0) -> sync_with_stdio(0);
    cin >> n >> c;
    t.rsz(n); d.rsz(n);
    F0R(i, n) {
        cin >> t[i] >> d[i];
        t[i] = t[i] - d[i] + 1;
        cur += t[i];
        if (t[i] % d[i] == 0) {
            ai nxt = {d[i], (t[i] / d[i])-1, i};
            events.pb(nxt);
            nxt = {d[i] - 1, 1, i+n};
            events.pb(nxt);
            nxt = {1, 1, i+n+n};
            events.pb(nxt);
        } else {
            ai nxt = {d[i], t[i] / d[i], i};
            events.pb(nxt);
            nxt = {t[i] % d[i], 1, i+n};
            events.pb(nxt);
        }
        r += t[i]/d[i] + 1;
    }
    sort(events.begin(), events.end());
    reverse(events.begin(), events.end());
    // for (ai e : events) cout << e[0] << ' ' << e[1] << ' ' << e[2] << '\n';
    if (cur <= c) {
        cout << "0\n";
        return 0;
    }
    fin.assign(2*n, false);
    cnt.assign(n, 0);
    while (l <= r) {
        int mid = (l+r)/2;
        if (check(mid)) {
            ans = mid;
            r = mid-1;
        } else l = mid+1;
    }
    cout << ans << '\n';
}