DAUGIA Pascal

var   a,b:longint;

function ktnt(x:longint):boolean;
var   i:longint;
begin
    if x<2 then exit(false);
    for i:=2 to trunc(sqrt(x)) do
           if x mod i=0 then exit(false);
    exit(true);
end;

function ktdx(x:longint):boolean;
var  i:longint;
       s:string;
begin
    str(x,s);
    for i:=1 to length(s) div 2 do
           if s[i]<>s[length(s)-i+1] then exit(false);
    exit(true);
end;

procedure xuli;
var   i,d:longint;
begin
    readln(a,b);d:=0;
    For i:=a to b do
           If (ktnt(i)=true) and (ktdx(i)=true) then inc(d);
    Writeln(d);

end;

begin
    assign(input,'daugia.inp');reset(input);
    assign(output,'daugia.out');rewrite(output);
    xuli;
    Close(input);Close(output);
end.