#include <bits/stdc++.h>

using namespace std;
ifstream f("branza.in");
ofstream g("branza.out");
int n,s,t,v[100005];
deque<int> d;
int main()
{
    f>>n>>s>>t;
    long long rez = 0;
    for(int i=1;i<=n;i++)
    {
        int cnt;
        f>>v[i]>>cnt;
        long long val = v[i]+1LL*(n-i)*s;
        while(!d.empty() && v[i]+1LL*(n-i)*s<v[d.back()]+1LL*(n-d.back())*s)
        {
            d.pop_back();
        }
        d.push_back(i);
        while(!d.empty() && d.front()<i-t)
        {
            d.pop_front();
        }
        rez+=1LL*cnt*(v[d.front()]+1LL*(i-d.front())*s);
    }
    g<<rez<<'\n';
    return 0;
}