n = int(input())
ab = [list(map(int, input().split())) for _ in range(n)]
ab.sort(key=lambda x: x[1], reverse=True)
dp = [[100000000000000000 for _ in range(n + 1)] for __ in range(n + 1)]
dp[0][0] = 0
for i in range(0, n):
    for j in range(0, i + 1):
        dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + ab[i][0] + ab[i][1] * (i - j))
        dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j])
print(dp[n][n//3])