#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import numpy as np


# %%
N = int(readline())
AB = np.array(read().split(), np.int64)
A = AB[::2]
B = AB[1::2]


# %%
ind = np.argsort(B)[::-1]
A = A[ind]
B = B[ind]

# %%
K = (N * 2 + 2) // 3
INF = 10 ** 15
dp = np.full(K + 1, INF, np.int64)
dp[0] = 0

for a, b in zip(A, B):
    np.minimum(dp[1:], dp[:-1] + (a + b * np.arange(K)), out=dp[1:])


# %%
print(dp[-1])