uses math;
const maxn = 2000;
var a,b:ansistring;
    k,i,j:longint;
    f: array[0..maxn,0..maxn] of longint;
begin
  readln(a);
  readln(b);
  while a[length(a)]=' ' do delete(a,length(a),1);
  while b[length(b)]=' ' do delete(b,length(b),1);
  readln(k);
  for i:=0 to length(a) do
  f[i,0]:=i*k;
  for i:=1 to length(b) do
  f[0,i]:=i*k;
  for i:=1 to length(a) do
  begin
    for j:=1 to length(b) do
    begin
      f[i,j]:=min(min(f[i-1,j]+k,f[i,j-1]+k),f[i-1,j-1]+abs(ord(a[i])-ord(b[j])));
    end;
  end;
  writeln(f[length(a),length(b)]);
end.

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Y21jIApzbm1uIAoy

cmc 
snmn 
2