var a:array[-5..100005] of longint;
n,max,i:longint;
begin
assign(input,'bai2.inp');reset(input);
assign(output,'bai2.out');rewrite(output);
readln(n);
for i:=1 to n do read(a[i]);
max:=a[1]+a[2]+a[3];
for i:=2 to n-2 do
if (a[i]+a[i+1]+a[i+2])>=max then max:=a[i]+a[i+1]+a[i+2];
write(max);
close(input);close(output);
end.