#include <bits/stdc++.h>
#define int long long
#pragma GCC optimize ("O3")
#define pb push_back
using namespace std;

signed main(){
    ifstream cin("branza.in");
    ofstream cout("branza.out");
    int n, s, t;cin >> n >> s >> t;
    vector<int> sigma1(n + 1), sigma2(n + 1);
    deque <int> dq;
    for(int i=1;i <= n;i++)cin >> sigma1[i] >> sigma2[i];
    int ss=0;
    for(int i=1;i <= n;i++){
        while(!dq.empty() && sigma1[dq.back()] - s * dq.back() >= sigma1[i] - s * i)
            dq.pop_back();
        dq.pb(i);
        if(dq.front() < i - t)
            dq.pop_front();
        ss += (sigma1[dq.front()] + s * (i - dq.front())) * sigma2[i];
    }
    cout << ss;
}     //6 7 https://codeforces.com/blog/entry/83467