N = int(input())
AB = [ tuple([int(j) for j in input().split()]) for _ in range(N)]
AB = sorted(AB, key=lambda x:x[1], reverse=True)

dp = [ [ 10**10 ]*(N+1) for _ in range(N+1)] # i,j iコメまで集めて、j 個タダでもらった
dp[0][0] = 0

for i in range(1,N+1):
    for j in range(0,N):
        dp[i][j] = min ( dp[i][j], dp[i-1][j] + AB[i-1][0] + AB[i-1][1]* (i-j-1))   
        dp[i][j+1] = min( dp[i-1][j], dp[i][j+1]) # タダで買う
    dp[i][N] = min(dp[i][N], dp[i-1][N] + AB[i-1][0] + AB[i-1][1]*(i-j-1))


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