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uses math;
var
f : text;
n : longint;
lena, i : integer;
a : array[1..512] of longint;
procedure insort(x : longint);
var i, j : integer;
begin
inc(lena);
a[lena] := x - 1;
for i := 1 to lena do
if a[i] < x then begin
for j := lena downto i + 1 do
a[j] := a[j - 1];
a[i] := x;
exit
end
end;
function notin(x : longint) : boolean;
var l, h, m : integer;
begin
l := 1;
h := lena;
repeat
m := (l + h) div 2;
if a[m] = x then exit(false);
if a[m] < x then h := m - 1
else l := m + 1
until l > h;
notin := true
end;
procedure mklist(n0 : longint);
var
i, j : byte;
n10, m0 : longint;
begin
if n0 <> 0 then begin
insort(n0);
for i := 0 to trunc(log10(n0)) do
begin
n10 := 1;
for j := 1 to i do n10 := n10 * 10;
m0 := n0 div (n10 * 10) + n0 mod n10;
if notin(m0) then mklist(m0)
end
end
end;
function prime(m : longint) : boolean;
var p, q : integer;
begin
if m < 2 then exit(false);
if m = 2 then exit(true);
if m = 3 then exit(true);
if m mod 2 = 0 then exit(false);
if m mod 3 = 0 then exit(false);
p := 5;
q := 2;
while p * p <= m do
begin
if m mod p = 0 then exit(false);
p := p + q;
q := 6 - q
end;
prime := true
end;
begin
assign(f, 'BAI1.INP');
reset(f);
read(f, n);
close(f);
lena := 0;
mklist(n);
assign(f, 'BAI1.OUT');
rewrite(f);
for i := 1 to lena do
if prime(a[i]) then begin
writeln(f, a[i]);
close(f);
exit
end;
writeln(f, -1);
close(f)
end.
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