回帖：贪心法，样例测试通过
program plan(input,output);
const maxn=1000;
var ans,i,j,n:longint;
left,right:array[1..maxn] of longint;
opt:array[1..maxn] of boolean;
procedure setio;
begin
assign(input,'plan.in');
assign(output,'plan.out');
reset(input);
rewrite(output);
end;
procedure swap(var a,b:longint);
var tmp:longint;
begin
tmp:=a;
a:=b;
b:=tmp;
end;
procedure init;
begin
readln(n);
for i:=1 to n do
begin
readln(left,right);
if left>right then
swap(left,right);
end;
fillchar(opt,sizeof(opt),true);
close(input);
end;
procedure solve;
procedure qsort;
procedure sort(l,r: longint);
var i,j,x,y: longint;
begin
i:=l;
j:=r;
x:=right[(l+r) div 2];
repeat
while rightj;
if l