#!/usr/bin/env python3

lines = (x.strip() for x in open("input.txt"))
signals = 0
x = 1
nxt = 20
pos = 0

for line in lines:
    pos += 2 if line[0] == 'a' else 1
    if pos >= nxt:
        signals += nxt * x
        nxt += 40
    if line[0] == 'a':
        x += int(line[5:])

print(signals)