import sys
sys.setrecursionlimit(20000000)
input = sys.stdin.readline
n = int(input())
a = [list(map(int,input().split())) for i in range(n)]
a.sort(key= lambda x: -x[1])
dp = [[float("inf")]*(n//3+1) for i in range(n+1)]
dp[0][0] = 0
for i in range(n):
        dp[i+1][0] = dp[i][0]+a[i][0]+a[i][1]*(i)
        for j in range(n//3):
                dp[i+1][j+1] = min(dp[i+1][j+1],dp[i][j],dp[i][j+1]+a[i][0]+a[i][1]*(i-j-1))

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