Chương trình 21

USES crt;
VAR n, i: INTEGER;
BEGIN
clrscr;
write('Nhap vao mot so nguyen: '); readln(n);
IF n<=1 THEN writeln(n,'khong la so nguyen to')
ELSE
BEGIN
i:=2;
WHILE (n MOD i <> 0) DO i:= i+1;
IF i = n THEN writeln(n,'la so nguyen to !')
ELSE writeln(n,'khong phai la so nguyen to!');
END;
readln
END.

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