[codevs2419]ISBN号码

var
s:string;
f:array[0..100] of longint;
i,j,k,l,n,ans:longint;

begin
readln(s);
for i:=1 to 10 do f[i]:=ord(s[i])-48;
if s[length(s)]='X' then f[10]:=10;
for i:=1 to 10 do if s[i]='?' then k:=i;
j:=10;
f[k]:=0;
for i:=1 to 10 do
begin
f[i]:=f[i]*j;
j:=j-1;
end;

//(10-k+1)
for i:=1 to 10 do ans:=ans+f[i];
if ans=0 then begin write(-1); exit; end;
for i:=0 to 9 do if (ans+i*(10-k+1)) mod 11=0 then
begin write(i); halt; end;

if (k=10) and ((ans+10) mod 11 =0) then begin write('X'); halt; end;
write(-1);
end.