n = int(input())
ab = [[int(i) for i in input().split()] for j in range(n)]

ab.sort(reverse=True, key=lambda x: x[1])
INF = 10**12

dp = [[INF]*(n+1) for i in range(n+1)]

dp[0][0] = 0

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

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