#include <iostream>
#include <fstream>
using namespace std;

long p[1000000],c[1000000],d[1000000];

long long st=0,dr=-1,sum,s,n,t;

ifstream f("branza.in");
ofstream g("branza.out");

int main()
{
    f>>n>>s>>t;
    for(int i=0;i<n;i++){
        f>>c[i]>>p[i];
        if(st<=dr && d[st]<=i-t)st++;
        while(st<=dr && c[i]<=c[d[dr]]+s*(i-d[dr]))dr--;
        d[++dr]=i;
        sum+=p[i]*(c[d[st]]+s*(i-d[st]));

    }
    g<<sum;
    return 0;
}