2 ladies and 2 girls need to cross a river in a boat big enough for 1 LADY or 2 girls. How do they do it?

GIRL and GIRL ->
<- GIRL
LADY ->
<- GIRL
GIRL and GIRL ->
<- GIRL
LADY ->
<- GIRL
GIRL and GIRL ->
2 ladies and 2 girls need to cross a river in a boat big enough for 1 LADY or 2 girls. How do they do it?
GIRL and GIRL ->
<- GIRL
LADY ->
<- GIRL
GIRL and GIRL ->
<- GIRL
LADY ->
<- GIRL
GIRL and GIRL ->