#include <cstdio>
#include <algorithm>
#include <deque>
#define Dim 100002

using namespace std;
int n, s, t, sol;
deque <int> d;
struct nod
{
    int p;
    int c;
}v[Dim];
void read()
{
    freopen("branza.in", "r", stdin);
    freopen("branza.out", "w", stdout);
    scanf("%d %d %d", &n, &s, &t);
    for(int i = 1; i <= n; ++ i)
    {
        scanf("%d %d", &v[i].p, &v[i].c);
        v[i].p += (n - i) * s;
    }
}
void solve()
{
    for(int i = 1; i <= n; ++ i)
    {
        if(d.front() < i - t + 1)
            d.pop_front();
        while(!d.empty() && v[i].p < v[d.back()].p)
            d.pop_back();
        d.push_back(i);
        sol += (v[d.front()].p - s * (n - i)) * v[i].c;
    }
}
void write()
{
    printf("%d\n", sol);
}
int main()
{
    read();
    solve();
    write();
    return 0;
}