NKCABLE pascal

var i,n: longint;
    a:array[1..25000] of longint;
    f:array[1..25000] of int64;
function min(s,d:int64):int64;
begin
        if s>d then exit(d);
        exit(s);
end;
procedure giai;
begin
    readln(n);
    for i:=1 to n-1 do
        readln(a[i]);
    f[2]:=a[1];
    f[3]:=a[1]+a[2];
    for i:=4 to n do
        f[i]:=min(f[i-1]+a[i-1],f[i-2]+a[i-1]);
     writeln(f[n]);
end;
begin
    assign(input,'nkcable.inp');reset(input);
    assign(output,'nkcable.out');rewrite(output);
    giai;
end.