milk.pas

Magio牛的usaco源代码

{
ID:maigoak1
PROG:milk
}

program milk;
const
  maxm=5000;
var
  fin,fout:text;
  n,money,tlong:longint;
  m,i,j,x,tint:integer;
  p:array[1..maxm]of integer;
  a:array[1..maxm]of longint;
begin
  assign(fin,'milk.in');
  reset(fin);
  readln(fin,n,m);
  for i:=1 to m do
    readln(fin,p[i],a[i]);
  close(fin);

  for i:=1 to m-1 do
    for j:=i+1 to m do
      if p[i]>p[j] then begin
        tint:=p[i];p[i]:=p[j];p[j]:=tint;
        tlong:=a[i];a[i]:=a[j];a[j]:=tlong;
      end;

  money:=0;x:=0;
  while n>0 do begin
    inc(x);
    if n<=a[x] then begin
      money:=money+p[x]*n;
      break;
    end;
    money:=money+p[x]*a[x];
    n:=n-a[x];
  end;

  assign(fout,'milk.out');
  rewrite(fout);
  writeln(fout,money);
  close(fout);
end.