【codevs】2918

var
codevs,poj:array[0..20] of longint;
ans,ci,pi,n,k,p,i:longint;
begin
readln(n,k,p);
for i:=1 to n do read(poj[i]);
readln;
for i:=1 to n do read(codevs[i]);
for i:=2 to n do poj[i]:=poj[i]+poj[i-1];
for i:=2 to n do codevs[i]:=codevs[i]+codevs[i-1];
ans:=-maxlongint;
for i:=0 to n-k do
begin
ci:=codevs[i+k]-codevs[i];
pi:=poj[i+k]-poj[i];
if ci-pi>ans then ans:=ci-pi;
end;
ans:=ans+1-p;
if ans<0 then writeln(-1)
else writeln(ans);
end.