These are the packages that would be merged, in order:

Calculating dependencies ...

!!! Problem resolving dependencies for =dev-ada/gnatdoc-25.0.0-r7
 done!
Dependency resolution took 0.83 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "=dev-ada/gnatdoc-25.0.0-r7" has unmet requirements.
- dev-ada/gnatdoc-25.0.0-r7::gentoo USE="-doc -static-libs -static-pic" ADA_TARGET="gcc_15 -gcc_12 -gcc_13 -gcc_14 (-gcc_16)" PYTHON_SINGLE_TARGET="-python3_12 -python3_13"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( python_single_target_python3_12 python_single_target_python3_13 )

  The above constraints are a subset of the following complete expression:
    exactly-one-of ( python_single_target_python3_12 python_single_target_python3_13 ) exactly-one-of ( ada_target_gcc_14 ada_target_gcc_15 )