import operator

lines = []
for line in open("input"):
    lines.append(line.split())


unused = lines
scope = {}
while unused:
    lines, unused = unused, []
    for words in lines:
        refs = [x for x in words[1:] if x.isalpha()]
        if any(r not in scope for r in refs):
            unused.append(words)
            continue
        dst = words[0].rstrip(':')
        if len(words) == 2:
            _, src = words
            scope[dst] = int(src)
            continue
        _, x, op, y = words
        scope[dst] = (op, scope[x], scope[y])

optab = {
    '*': operator.mul,
    '/': operator.floordiv,
    '+': operator.add,
    '-': operator.sub,
}

def eval(x):
    if type(x) == int:
        return x
    op = x[0]
    args = [eval(a) for a in x[1:]]
    return optab[op](*args)

print(eval(scope['root']))