program ex_2;
uses math;
var f:array[-3..40000] of longint;
    m:array[1..40000] of longint;
    d,n,i,k,l,j:longint;
    total:int64;
begin
  assign(input,'optmilk.in'); reset(input);
  assign(output,'optmilk.out'); rewrite(output);
  readln(n,d);
  for i:=1 to n do
  begin
    readln(m[i]);
  end;
  total:=0;
  for i:=1 to n do
  begin
    f[i]:=max(f[i-2],f[i-3])+m[i];
  end;
  for i:=1 to d do
  begin
    readln(k,l);
    m[k]:=l;
    for j:=k to n do
    begin
      f[j]:=max(f[j-2],f[j-3])+m[j];
    end;
    total:=total+max(f[n-1],f[n]);
  end;
  writeln(total);
  close(input); close(output);
end.