#include <bits/stdc++.h>

using namespace std;

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

deque <int> q;
long long n, s, t, c[100005], p[100005], cmin;

int main()
{
    fin >> n >> s >> t;
    for (int i=1; i<=n; i++)
        fin >> c[i] >> p[i];
    for (int i=1; i<=n; i++)
    {
        while (!q.empty() && c[q.back()]+s*(i-q.back())>=c[i])
            q.pop_back();
        q.push_back(i);
        if (!q.empty() && i-q.front()>t)
            q.pop_front();
        cmin+=c[q.front()]*p[i]+s*(i-q.front())*p[i];
    }
    fout << cmin;
    return 0;
}