记录编号	2067	评测结果	AAAAAAAAAA
题目名称	驾车旅行	最终得分	100
用户昵称	WaterFire	是否通过	通过
代码语言	Pascal	运行时间	0.008 s
提交时间	2008-09-11 21:53:04	内存使用	0.00 MiB

program waterfire;
const
fin='tour.in';
fout='tour.out';
var
ans,maxl,maxv,lc,bc,p:real;
n,i,j:longint;
ss,l,c:array[0..51] of real;

procedure Init;
var
i:longint;f:text;
begin
assign(f,fin);reset(f);
readln(f,maxl);
read(f,maxv,lc,bc,n);
for i:=1 to n do
readln(f,l[i],c[i]);
close(f);
ss[0]:=maxv;l[0]:=0;c[0]:=bc/maxv;
ss[1]:=maxv-l[1]/lc;l[n+1]:=maxl;
ans:=maxlongint;
end;

procedure search(x:longint);
var
i,j,r:longint;
begin
if x=n+1 then begin
if p<ans then ans:=p;  exit;
end;
      for r:=0 to 1 do
           if r=0 then  begin
               if ss[x]*lc>l[x+1]-l[x] then begin
                  ss[x+1]:=ss[x]-(l[x+1]-l[x])/lc;
                  search(x+1);
                  ss[x+1]:=ss[x]+(l[x+1]-l[x])/lc;
               end;
           end;
           if r=1 then begin
                if not((ss[x]*lc>l[x+1]-l[x])and(ss[x]>maxv/2)) then
                   begin
                   ss[x+1]:=maxv-(l[x+1]-l[x])/lc;
                   p:=p+(maxv-ss[x])*c[x]+20;
                   search(x+1);
                   p:=p-(maxv-ss[x])*c[x]-20;
                   end;
           end;
 end;

procedure print;
var
i,j:longint;
f:text;
begin
ans:=ans+bc;
assign(f,fout);rewrite(f);
write(f,ans:0:1);
close(f);
end;

begin
Init;
search(1);
print;
end.