n = int(input())
ab = [list(map(int,input().split())) for _ in range(n)]
ab.sort(key=lambda x:x[1], reverse=1)
# dp[i][x] = i まで見て購入 x 個
N = n//3*2 + [0,1,2][n%3]
INF = 1<<50
dp = [INF]*(N+1)
dp[0] = 0
for a,b in ab:
    for i in range(1,N+1)[::-1]:
        dp[i] = min(dp[i],dp[i-1]+a+b*(i-1))
print(dp[-1])