# Naming

- `s` denotes a source vertex.
- `t` denotes a target vertex.
- `u` denotes a tail vertex or the first vertex in scope.
- `v` denotes a head vertex or the second vertex in scope.
- `w` denotes the weight of an arc.
- `x` denotes a tail vertex or the third vertex in scope.
- `y` denotes a head vertex or the fourth vertex in scope.
