import sys import re def selfprint(x): print(x) return x def one_by_one(inputf): return ([int(__) for __ in _.split()] for _ in (re.sub("[:]", " ", _) for _ in (_.strip() for _ in iter(inputf)) if _)) def scanner_pos(tick, depth): x = depth - 1 p = x - abs(x - tick % (2*x)) return p def positions(tick, firewalls): return ((_, scanner_pos(tick + _[0], _[1])) for _ in firewalls) def collisions(tick, firewalls, pos): return ((f, p == pos) for f, p in positions(tick, firewalls) if p == pos) def has_next(seq): return next((True for _ in seq), False) def compute_weight(seq): return sum((f[0] * f[1] for f,_ in seq)) with sys.stdin as f: firewalls = list(one_by_one(f)) print(compute_weight(collisions(0, firewalls, 0)))