#include <bits/stdc++.h>
using namespace std;
long long T,N,L,R,X,K,now_idx,now_speed,now_time,now_set,x,y;
int main(){
	cin>>T>>N>>L>>R>>X>>K;
	now_idx=1;
	now_speed=L;
	while(T--){
		cin>>x>>y;
		if(x==0){
			now_idx++;
			now_speed=L;
			if(now_idx>N){
				cout<<-1;
				return 0;
			}
		}
		else if(x==1){
			now_idx--;
			now_speed=R;
			if(now_speed<=0){
				cout<<-1;
				return 0;
			}
		}
		if(y==1) now_speed=min(now_speed+X,R);
		if(now_speed==R) now_time++;
		else now_time=0;
		now_set+=now_speed*now_idx;
		if(now_time==K){
			cout<<now_set;
			return 0;
		}
	}
	cout<<now_set;
	return 0;
}