#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N, S;
    cin >> N >> S;
    vector<pair<ll, int>> events;
    ll sum_d = 0;
    for (int i = 0; i < N; ++i) {
        ll H, V;
        cin >> H >> V;
        ll d = abs(H);
        sum_d += d;
        if (d < S) {
            events.push_back({V - S, 1});
            events.push_back({V - d, -2});
            events.push_back({V, 2});
            events.push_back({V + d, -2});
            events.push_back({V + S, 1});
        } else {
            events.push_back({V - d, -1});
            events.push_back({V, 2});
            events.push_back({V + d, -1});
        }
    }
    sort(events.begin(), events.end());
    // 合并相同坐标的事件
    vector<pair<ll, int>> merged;
    for (auto &e : events) {
        if (merged.empty() || merged.back().first != e.first) {
            merged.push_back(e);
        } else {
            merged.back().second += e.second;
        }
    }
    const ll L = -4000000000LL; // 足够小的初始位置
    ll prev_x = L;
    ll f = sum_d;
    ll A = 0;
    ll ans = f;
    for (auto &e : merged) {
        ll x = e.first;
        int delta = e.second;
        f += A * (x - prev_x);
        if (f < ans) ans = f;
        A += delta;
        prev_x = x;
    }
    cout << ans << endl;
    return 0;
}