n = int(input())
AB = []
for i in range(n):
    a, b = map(int, input().split())
    AB.append((a, b))
AB.sort(key=lambda x: -x[1])
INF = 10**18
dp = [INF]*(n+1)
dp[0] = 0
for i, (a, b) in enumerate(AB):
    nx = [INF]*(n+1)
    for j in range(n):
        if j >= 1:
            nx[j] = min(nx[j], dp[j-1], dp[j]+a+b*(i-j))
        else:
            nx[j] = min(nx[j], dp[j]+a+b*(i-j))
    dp = nx
print(dp[n//3])