program de;
   var
   a,n,i,r,x,y,step,j:longint;
   q:boolean;
   s1,s2,s:string;
begin
  step:=1;
  q:=false;
  read(x);
  read(y);
  repeat
    s1:='';
    s2:='';
    n:=x;
    inc(step);
    repeat
     i:=n mod step;
     n:=n div step;
     str(i,s);
     s1:=s+s1;
    until n=0;
    r:=y;
    repeat
     i:=r mod step;
     r:=r div step;
     str(i,s);
     s2:=s+s2;
    until r=0;
    j:=1;
    for i:=1 to length(s1) do
     if (s1[i]=s2[j]) and (j<>length(s2)+1) then inc(j);
    if j=length(s2)+1 then q:=true;
  until (step=x+1) or q;
  if q then writeln(step)
  else writeln('No solution');
end.

For test 11 10
Your program writes 11
My AC program writes 'No solution'

My AC program uses bases from 2 to 100000

How to organize translation in other system of calculation, it is more 9

Part of my AC program:

leny = lenx = 0;
while (x > 0)
  ax[lenx++] = x % base, x /= base;
while (y > 0)
  ay[leny++] = y % base, y /= base;

x, y - decimal numbers
base - system of calculation
ax[], ay[] - x and y in new system
lenx, leny - its lengths