#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const ll MAXN = 1e9 + 1;

map<ll, ll> h;

ll ans = 0;

bool check_cur_ans(ll T, ll H, ll x) {
    ll t = 0;
    ll current_h = 0;
    while (current_h < H) {
        current_h += x;
        t++;
        if (t > T) {
            return false;
        }

        auto it = h.end()--;
        for (it; it != h.begin(); it--) {
            if (current_h < it->first) {
                continue;
            }
            current_h -= min(it->second, current_h - it->first + 1);
        }

        it = h.begin();
        if (current_h < it->first) {
            continue;
        }
        else {
            current_h -= min(it->second, current_h - it->first + 1);
        }
    }
    return true;
}


void bin_search (ll left, ll right, ll T, ll H, ll mid = 0) {
    while (right - left > 0) {
        mid = (left + right) >> 1;

        if ((check_cur_ans(T, H, mid))) {
            right = mid;
        }
        else {
            left = mid + 1;
        }
    }

    ans = right;
}

void solve() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    ll n, H, T;
    cin >> n >> H >> T;

    for (int i = 1; i <= n; i++) {
        ll a, b;
        cin >> a >> b;
        h[a] = b;
    }

    ll left = 1;
    ll right = MAXN;

    bin_search(left, right, T, H);

    cout << ans;
}

int main() {
    solve();
    return 0;
}