find letter series {a , bc, def, ghij, klmno __________________________ a-z}

a!forEach(
  items: enumerate(8),
  expression: joinarray(
    a!forEach(
      items: enumerate(fv!index) + sum(enumerate(fv!index)) + 1,
      expression: index(
        "abcdefghijklmnopqrstuvwxyz",
        fv!item,
        {}
      )
    )
  )
)

a!forEach(
  items: enumerate(8),
  expression: joinarray(
    a!forEach(
      items: enumerate(fv!index) + sum(enumerate(fv!index)) + 1,
      expression: index(
        "abcdefghijklmnopqrstuvwxyz",
        fv!item,
        {}
      )
    )
  )
)

thank you