1061D - TV Shows.cpp

#include <iostream>
#include <string>
#include <utility>
#include <sstream>
#include <algorithm>
#include <stack>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <bitset>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <unordered_set>

using namespace std;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define F0R1(i, a) for (int i=1; i<=(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define F0Rd1(i, a) for (int i=a; i>0; i--)
#define SORT(vec) sort(vec.begin(), vec.end())

#define INF 1000000010
#define LL_INF 4500000000000000000
#define LSOne(S) (S & (-S))
#define EPS 1e-9
#define pA first
#define pB second
#define mp make_pair
#define pb push_back
#define PI acos(-1.0)
#define ll long long
#define MOD (int)(2e+9+11)
#define SET(vec, val, size) for (int i = 0; i < size; i++) vec[i] = val;
#define SET2D(arr, val, dim1, dim2) F0R(i, dim1) F0R(j, dim2) arr[i][j] = val;
#define SET3D(arr, val, dim1, dim2, dim3) F0R(i, dim1) F0R(j, dim2) F0R(k, dim3) arr[i][j][k] = val;
#define SET4D(arr, val, dim1, dim2, dim3, dim4) F0R(i, dim1) F0R(j, dim2) F0R(k, dim3) F0R(l, dim4) arr[i][j][k][l] = val;
#define READGRID(arr, dim) F0R(i, dim) F0R(j, dim) cin >> arr[i][j];
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vl;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    ll n, x, y; cin >> n >> x >> y;
    ll magic = x / y;
    pll A[n]; F0R(i, n) cin >> A[i].pA >> A[i].pB;
    sort(A, A+n);

    // stores end time of each tv
    multiset<ll> B;
    ll ans = 0;
    for (pll a : A) {
        bool newTV = false;
        if (B.size() == 0) {
            newTV = true;
        } else {
            auto it = B.begin();
            ll best = -1;
            while (it != B.end()) {
                ll nextEnd = *it;
                if (a.pA <= nextEnd) break;
                if (a.pA - nextEnd > magic) {
                    it = B.erase(it);
                } else {
                    best = nextEnd;
                    it++;
                }
            }
            if (best == -1) {
                newTV = true;
            } else {
                // reuse TV
                ans += (a.pB-best)*y;
                B.erase(--it);
                B.insert(a.pB);
            }
        }
        if (newTV) {
            ans += x + (a.pB - a.pA) * y;
            B.insert(a.pB);
        }
        ans %= (ll)1e+9+7;
    }
    cout << ans << endl;

    return 0;
}