#include <iostream>
#define FIN "branza.in"
#define FOUT "branza.out"
#define MAX 100010
using namespace std;
long long rez;
long long C[MAX],P[MAX];
long long S,T,N;
long long deq[MAX],ind[MAX],time[MAX];
long long m[MAX];


void iofile(void){

	freopen(FIN,"rt",stdin);
	freopen(FOUT,"wt",stdout);

	scanf("%lld%lld%lld",&N,&S,&T);
	for (int i=1;i<=N;++i){
		scanf("%lld%lld",&C[i],&P[i]);
	}

	fclose(stdin);
	return ;
}

void solve(void){

	int p=1;
	int u=0;
	rez=0;
	for (int i=1;i<=N;++i){
		for (;p<=u && time[p]==i;++p);
		++u;
		deq[u]=C[i]+(N-i)*S;
		time[u]=i+T+1;
		ind[u]=i;
		for (;u>p && deq[u]<deq[u-1];--u){
			deq[u-1]=deq[u];
			time[u-1]=time[u];
			ind[u-1]=ind[u];
		}
		long long rel=ind[p];
		m[i]=C[rel]+(i-rel)*S;
		rez+=m[i]*P[i];
	}

	printf("%lld\n",rez);
	fclose(stdout);
	return ;
}

int main(void){

	iofile();
	solve();
	return 0;
}