/DAUGIA - Đấu giá (OLP Không chuyên 2010)

              USES CRT;
        var     NT:array[1..5000000] of boolean;
                a,b,i,dem:longint;
PROCEDURE ERAS;
var i,temp1:longint;
begin
    fillchar(NT,sizeof(NT),true);
    for i:=2 to 316 do
    if NT[i]=true then begin
        temp1:=i;
        while temp1<=100000 do begin
            inc(temp1,i);
            NT[temp1]:=false;
        end;
    end;
end;
FUNCTION PALIN (n:longint):boolean;
var i:longint;
    s:string;
begin
    str(n,s);
    for i:=1 to length(s) do
    if s[i]<>s[length(s)-i+1] then exit(false);
    exit(true);
end;
                begin
                    ERAS;
                    readln(a,b);
                    dem:=0;
                    for i:=a to b do
                    if (NT[i]) and (PALIN(i)) then inc(dem);
                    writeln(dem);
                    readln
                end.