n = int(input())
t = [(0, 0)] +  sorted([tuple(map(int, input().split())) for _ in range(n)], key=lambda x:-x[1])
inf = float("inf")

dp = [[inf]*(n+2) for _ in range(n+1)]
dp[0][0] = 0

for i in range(1, n+1):
    dp[i][0] = dp[i-1][0]+t[i][0]+t[i][1]*(i-1)

for i in range(1, n+1):
    for j in range(1, n+1):
            dp[i][j] = min(dp[i-1][j-1], dp[i-1][j]+t[i][0]+t[i][1]*(i-j-1))

print(dp[n][n//3])