n = int(input())
ab = [list(map(int, input().split())) for _ in range(n)]
ab.sort(key=lambda x:-x[1])
cnt = n // 3 * 2
cnt += n % 3
dp = [[1 << 60] * (cnt + 1) for _ in range(n + 1)]
dp[0][0] = 0
for i, (a, b) in enumerate(ab, 1):
    for j in range(cnt, -1, -1):
        dp[i][j] = dp[i - 1][j]
        if j != 0:
            dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + a + b * (j - 1))
print(dp[-1][-1])