Program machine;
Uses Math;
{ constraints }
const
    MAXD = 1000;

{ input data }
var
    C, D, Y, i,j,acquisti,costo, costominimo  : longint;
    // Warning! M and P are 1-based
    M, P        : array[1..MAXD] of longint;
    bilancio : array[0..2000] of longint;

begin

   (* assign(input,  'input.txt');  reset(input);
    assign(output, 'output.txt'); rewrite(output);*)


    readln(C, D, Y);
     // Warning! M and P are 1-based
    for i:=1 to D do
        read(M[i]);
    readln();
    for i:=1 to D do
        read(P[i]);
    readln();
    for i:=0 to Y do bilancio[i]:=2000000;
    bilancio[1]:=C+M[1]-P[1]; 
    { insert your code here }
    bilancio[0]:=0; costo:=0; 
    for i := 1 to D do
              begin
                  costo := costo +M[i]+P[i-1]-P[i];
                  costominimo := costo+C;
                  for j := 1 to i div 2 do
                         begin 
                           costominimo:= min(costominimo, bilancio[j]+bilancio[i-j]);
                           bilancio[i] :=costominimo;
                         end;  
              end;
   for i := D+1 to Y do
              begin
                 costominimo := bilancio[1]+bilancio[i-1];
                 for j := 2 to j div 2 do
                       begin
                          costominimo := min(costominimo, bilancio[j]+bilancio[i-j]);
                          bilancio[i] := costominimo;
                       end;
              end;
   
    costominimo:=bilancio[1]* Y; 
    for i:=2 to Y do costominimo := min(costominimo, (Y div i)*bilancio[i] + bilancio[Y mod i]);
      
    writeln(costominimo);   { print result }
end.