from lib import *

data = open(0).read()

part_2 = False
if part_2:
    gates = {"b": 16076}
else:
    gates = {}

while "a" not in gates:
    for line in data.splitlines():
        lhs, rhs = line.split(" -> ")
        if part_2 and rhs == "b":
            continue
        lhs = lhs.strip()
        if "NOT" in lhs:
            op, op1 = lhs.split(" ")
            assert op == "NOT"
            try:
                op1 = int(op1)
                gates[rhs] = ~op1 & 0xffff
            except ValueError:
                if op1 in gates and isinstance(gates[op1], int):
                    gates[rhs] = ~gates[op1] & 0xffff
        elif "OR" in lhs:
            op1, op, op2 = lhs.split(" ")
            assert op == "OR"
            try:
                op1 = int(op1)
            except ValueError:
                if op1 in gates and isinstance(gates[op1], int):
                    op1 = gates[op1]
            try:
                op2 = int(op2)
            except ValueError:
                if op2 in gates and isinstance(gates[op2], int):
                    op2 = gates[op2]

            if not (isinstance(op1, int) and isinstance(op2, int)):
                continue
            gates[rhs] = (op1 | op2) 
        elif "AND" in lhs:
            op1, op, op2 = lhs.split(" ")
            assert op == "AND"
            try:
                op1 = int(op1)
            except ValueError:
                if op1 in gates and isinstance(gates[op1], int):
                    op1 = gates[op1]
            try:
                op2 = int(op2)
            except ValueError:
                if op2 in gates and isinstance(gates[op2], int):
                    op2 = gates[op2]

            if not (isinstance(op1, int) and isinstance(op2, int)):
                continue
            gates[rhs] = (op1 & op2) 
        elif "LSHIFT" in lhs:
            op1, op, op2 = lhs.split(" ")
            op2 = int(op2)
            try:
                op1 = int(op1)
            except ValueError:
                if op1 in gates:
                    op1 = gates[op1]
                else:
                    continue
            gates[rhs] = (op1 << op2) & 0xffff
        elif "RSHIFT" in lhs:
            op1, op, op2 = lhs.split(" ")
            op2 = int(op2)
            try:
                op1 = int(op1)
            except ValueError:
                if op1 in gates:
                    op1 = gates[op1]
                else:
                    continue
            gates[rhs] = (op1 >> op2) & 0xffff
        else:
            try:
                lhs = int(lhs)
                gates[rhs] = lhs
            except ValueError:
                if lhs in gates:
                    gates[rhs] = gates[lhs]

print(gates["a"])