employees has columns employee_id, first_name and salary.
Return the five highest-paid employees, plus anybody tied with the fifth, so
the result can be longer than five rows. Sort by salary descending then
employee_id, and renumber the index from 0.
nlargest cuts at exactly five by default; it takes a keep argument that
changes what happens at the boundary.
Input
employee_id first_name salary
0 1 A 100
1 2 B 90
2 3 C 80
3 4 D 70
4 5 E 60
5 6 F 60
6 7 G 50
Output
employee_id first_name salary
0 1 A 100
1 2 B 90
2 3 C 80
3 4 D 70
4 5 E 60
5 6 F 60