Program baitap;
Uses crt;
Var A:array[1..50] of real;
    i,n:integer;
    max:real;
Begin
Clrscr;
Write('So hoc sinh:'); Readln(n);
For i:=1 to n do 
     Begin
     Write('Dime ban thu ',i,':');
     Readln(A[i]);
     End;
max:=A[1];
For i:=2 to n do 
 If A[i]>max then max:=A[i];
Writeln('Diem cao nhat:',max:2:1);
Readln
End.

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Đã test code

uses crt;
 var a : array[1..100] of real ;
   n, i : integer ;
    max : real ;
  begin 
   clrscr;
    write('Nhap so luong hoc sinh: ');
     readln(n);
for i := 1 to n do
     begin
    write('Nhap diem cua hoc sinh thu ',i,' bang: ');
    readln(a[i]);
     end ;
max := a[1];
  for i := 2 to n do
    if max < a[i] then max := a[i];
   writeln('Hoc sinh co diem cao nhat la: ',max:3:2);
      end .