
PASS "1" becomes "1"
PASS "+1" becomes "1"
PASS "-1" becomes "-1"
PASS "0n + 0" becomes "0"
PASS "0n + 1" becomes "1"
PASS "0n - 1" becomes "-1"
PASS "1n" becomes "n"
PASS "1n - 0" becomes "n"
PASS "1n + 1" becomes "n+1"
PASS "1n - 1" becomes "n-1"
PASS "-1n" becomes "-n"
PASS "-1n - 0" becomes "-n"
PASS "-1n + 1" becomes "-n+1"
PASS "-1n - 1" becomes "-n-1"
PASS "+n+1" becomes "n+1"
PASS "-n-1" becomes "-n-1"
PASS "n + 0" becomes "n"
PASS "n - 0" becomes "n"
PASS "2n + 2" becomes "2n+2"
PASS "-2n - 2" becomes "-2n-2"