*Tăng
uses crt;
var i,j,n,result:longint;
a,f:array[1..1000000] of longint;
function max(a,b:longint):longint;
begin
if a>b then exit(a);
exit(b);
end;
begin
clrscr;
readln(n);
for i:=1 to n do read(a[i]);
f[1]:=1;
for i:=2 to n do
begin
f[i]:=0;
for j:=1 to i-1 do
if a[j]+1=a[i] then
f[i]:=max(f[i],f[j]+1);
result:=max(f[i],result);
end;
writeln(result);
readln;readln;
end.
=======================
*Giảm
uses crt;
var i,j,n,result:longint;
a,f:array[1..1000000] of longint;
function max(a,b:longint):longint;
begin
if a>b then exit(a);
exit(b);
end;
begin
clrscr;
readln(n);
for i:=1 to n do read(a[i]);
f[1]:=1;
for i:=2 to n do
begin
f[i]:=0;
for j:=1 to i-1 do
if a[j]=a[i]+1 then
f[i]:=max(f[i],f[j]+1);
result:=max(f[i],result);
end;
writeln(result);
readln;readln;
end.
