#!/usr/bin/env python3
from typing import Generator, Any

lines = (x.strip() for x in open("input.txt"))
root = dict()
sizes = []

def parse(obj: dict, gen: Generator[str, Any, None]):
    for line in gen:
        if line == '$ ls' or line == "$ cd /":
            continue
        elif line == "$ cd ..":
            return obj
        elif line[:4] == "$ cd":
            parse(obj[line[5:]], gen)
        elif line[0] == "d":
            obj[line[4:]] = dict()
        else:
            size, name = line.split(" ", 1)
            obj[name] = int(size)
    return obj

def calc(obj: dict, sizes: list):
    s = sum(v if isinstance(v, int) else calc(v, sizes) for v in obj.values())
    sizes.append(s)
    return s

parse(root, lines)
root_size = calc(root, sizes)

free_up = root_size - 40000000
print(next(i for i in sorted(sizes) if i > free_up))