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

ifstream fin("branza.in");
ofstream fout("branza.out");

int main() {

    int n, s,t;
    fin>>n>>s>>t;

    vector<pair<int,int>> a(n + 1);

    for (int i = 1; i <= n; i++)
        fin >>a[i].second>>a[i].first;

    deque<int> dq;

    int rez = 0;

    for (int i = 1; i <= n; i++) {

        long long base_i = a[i].second - 1LL * s * i;

        while (!dq.empty() && a[dq.back()].second - 1LL * s * dq.back() > base_i)
            dq.pop_back();

        dq.push_back(i);

        if (!dq.empty() && dq.front() < i - t)
            dq.pop_front();

        rez += (a[dq.front()].second - 1LL * s * dq.front() + 1LL * s * i) * a[i].first;
    }

    fout<<rez;

    return 0;
}


/**#include <iostream>
#include <bits/stdc++.h>
using namespace std;

ifstream fin("secventa.in");
ofstream fout("secventa.out");

int main()
{

    int n,k;
    fin>>n>>k;

    multiset<int>st;

    int rez = -1e9,l,r;

    vector<int>a(n+1);
    a[0] = -1e9;

    deque<int>dq;

    for(int i=1;i<=n;i++)
        fin>>a[i];

    for(int i=1;i<=n;i++){

        while(!dq.empty() && a[dq.front()] > a[i])
            dq.pop_front();

        if(dq.empty())
            dq.push_front(i);

        if (i >= k) {

            int curMin = a[dq.front()];
            int start = i - k + 1;
            int sf = i;
            if (curMin > rez || (curMin == rez && (start < l || (start == l && sf < r)))) {
                rez = curMin;
                l = start;
                r = sf;
            }
        }
    }

    fout<<l<<" "<<r<<" "<<rez;

    return 0;
}*/