Dequisonguyento

{De qui so nguyen to}
Program dq_snt;
uses crt;
var n,i:integer;F1,F2:text;
Function snt(n,i:integer):Boolean;
     begin
     If i=1 then snt:=True
     else if (n mod i=0) then snt:=False else
     snt:=snt(n,i-1);
     end;
     begin
     clrscr;
     Assign(F1,'snt.inp');Reset(F1);  Assign(F2,'snt.out'); Rewrite(F2);
     Read(F1,n); Close(F1);
     If snt(n,n-1)=true then Write(F2,n,' la so nguyen to') else
     WRite(F2,n,' khong phai la so nguyen to'); Close(F2);
     readln
     end.