#include <iostream>
#include <fstream>
#include <queue>
#include <set>
using namespace std;
ifstream in("branza.in");
ofstream out("branza.out");
const int maxn = 100005;
deque <int> dq;
int C[maxn];
int P[maxn];
int S;

inline int fast(int poz)
{
    return C[poz] - poz * S;
}

int main()
{
    int n, t;
    in >> n >> S >> t;
    for(int i = 1; i <= n; i++)
        in >> C[i] >> P[i];
    unsigned long long ans = 0;
    for(int i = 1; i <= n; i++)
    {
        while(!dq.empty() && fast(i) <= fast(dq.back()))
            dq.pop_back();
        dq.push_back(i);
        while(!dq.empty() && i - dq.front() > t)
            dq.pop_front();
        int aux = dq.front();
        ans = ans + 1LL * P[i] * (i * S + fast(aux));
    }
    out << ans << "\n";
    return 0;
}