import sys
from math import ceil
from operator import itemgetter
N = int(input())
items = sorted((tuple(map(int, l.split())) for l in sys.stdin), key=itemgetter(1), reverse=True)
count = ceil(2/3*N)
inf = 10**12
dp = [0] + [inf]*count

for i, (a, b) in enumerate(items, start=1):
    for j in range(min(count, i), 0, -1):
        dp[j] = min(dp[j], dp[j-1]+a+b*(j-1))

print(dp[-1])