求1+4+7+...+298

program dsk1;
var
  s, i:integer;
begin
s := 1;
for i := 1 to 99 do
  s := s+i*3+1;
writeln(s);
end.

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program dsk1;
const e = 298;
var
  s, i : integer;
  begin
  s := 1;
  for i := 1 to e div 3 do
      s := s+i*3+1;
  writeln('sum: ', s);
  readln;
end.

========================================================

program dsk1;
const e = 298;
var
  s, i : integer;
begin
  s := 0;
  for i := 1 to e div 3 do
      s := s+i;
  writeln('sum: ', s*3 + e div 3 + 1);
  readln;
end.