import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	items = []
	for i in range(N):
		A, B = getlist()
		items.append([B, A])

	items.sort(reverse = True)

	day = None
	if N % 3 == 0:
		day = int(N * 2 // 3)
	elif N % 3 == 1:
		day = int(N // 3) * 2 + 1
	else:
		day = int((N + 1) * 2 // 3)

	DP = [[INF] * (N + 1) for i in range(N + 1)]
	DP[0][0] = 0
	for i in range(N):
		b, a = items[i]
		for j in range(N):
			DP[i + 1][j] = min(DP[i + 1][j], DP[i][j])
			DP[i + 1][j + 1] = min(DP[i + 1][j + 1], DP[i][j] + a + j * b)

	# print(DP)
	ans = DP[N][day]
	print(ans)

if __name__ == '__main__':
	main()