N = int(input())
AB = [list(map(int, input().split())) for _ in range(N)]
N1 = N - N // 3
dp = [[0] * (N // 3 + 1) for _ in range(N)]
AB.sort(key=lambda x: x[1])
for i in range(N):
    a, b = AB[i]
    for j in range(N // 3 + 1):
        if i - j < N1:
            dp[i][j] = dp[i - 1][j] + a + b * (N1 - i + j - 1)
        if j > 0:
            dp[i][j] = min(dp[i][j], dp[i - 1][j - 1])
print(dp[-1][-1])