C++ :

#include <cstdio>
#include <cstring>
#include <cmath>
#include <climits>
#include <cstdlib>
#include <algorithm>
#define MAXN 50010
#define LL long long
using namespace std;

int N=0,S=0,T=0;
int C[MAXN]={0},P[MAXN]={0}; 
int Q[MAXN*10]={0};

int head=1,tail=0;

inline int Get(int p){
	while(head<=tail && p-Q[head]>T) head++;
	return Q[head];
}

inline void Push(int x){
	while(head<=tail && S*(x-Q[tail])+C[Q[tail]] >C[x] ) tail--;
	Q[++tail]=x;
}

int main(){
	//freopen("pudding.in","r",stdin);
	//freopen("pudding.out","w",stdout);
	
	scanf("%d%d%d",&N,&S,&T);
	for(int i=1;i<=N;++i)	scanf("%d%d",&C[i],&P[i]);		
	
	/*暴力！！！ 
	for(int i=1;i<=N;++i){
		for(int j=1;j<=T && i+j<=N;++j){
			if(C[i]+S*j < C[i+j]){
				C[i+j]=C[i]+S*j;
			}
		}
	}
	LL Ans=0;
	for(int i=1;i<=N;++i)	Ans+=P[i]*C[i];*/
	
	LL Ans=0;	int pos;
	for(int i=1;i<=N;++i){
		Push(i);	pos=Get(i);
		Ans+=P[i]*(S*(i-pos)+C[pos]);
	}
	
	printf("%lld",Ans);
	
	fclose(stdin);
	fclose(stdout);
	return 0;
}