##
# Show how to implement big number multiplication (even though Icon and Unicon
# handle big numbers transparently...)
global dpw, maxs

procedure main()
   dpw := 10
   maxs := 10^dpw
   every (n1|n2) := cvt2bn(2^64)
   write(2^64)
   write(2^64*2^64)  # How one really does multiply in Icon and Unicon
   write(bn2str(bnmult(n1,n2)))  # How this challenge wants it done
end

procedure bnmult(n1,n2)
   n := [0]
   k := 1
   if *n1 > *n2 then n1 :=: n2
   every i := 1 to *n1 do {
      every j := 1 to *n2 do {
         if k > *n then put(n,0)
         x := n1[i]*n2[j]
         r := x/maxs
         n[k] +:= x%maxs
         if r > 0 then {
            if k = *n then put(n,0)
            n[k+1] +:= r
            }
         k +:= 1
         }
      k := i+1
      }
   return n
end

procedure cvt2bn(n)
   bn := []
   while (n > 0, put(bn,n%maxs), n /:= maxs)
   return bn
end

procedure bn2str(bn)
   s := ""||bn[-1]
   every s ||:= right(bn[*bn-1 to 1 by -1],dpw,"0")
   return s
end