#include<fstream>
using namespace std;
const int N=100001;


struct branza{ int c,p;};
branza v[N];
int d[N],s,t,n,i,st,dr;


inline void stanga(int i)
{
	if(d[dr]==i-t)
		st++;
}

inline void dreapta(int i)
{
	while(st<=dr  &&  v[d[dr]].c + (long long)(i-d[dr])*s>=v[i].c)
	{
		--dr;
	}
}
	
inline void adauga(int i)
{
	d[++dr]=i;
}
ifstream in("branza.in");
ofstream out("branza.out");

int main()
{
	long long pc=0;
	in>>n>>s>>t;
	
	for(i=1;i<=n;i++)
		in>>v[i].c>>v[i].p;
	
	st=1;
	dr=0;
	t++;
	for(i=1;i<=n;i++)
	{
		stanga(i);
		dreapta(i);
		adauga(i);
		pc+=(v[d[st]].c + (long long)(i - d[st])*s)*v[i].p;
	}
	out<<pc;
	return 0;
}

	
//problemele secventa, secvdist, knumere;