N = int(input())
item = [list(map(int, input().split())) for _ in range(N)]
item.sort(reverse=True,key = lambda x:x[1])

dp = [float('inf')]*(N-N//3+1)
dp[0] = 0
for i in range(N):
    a,b = item[i]
    ndp = [float('inf')]*(N-N//3+1)
    ndp[0] = 0
    for j in range(1,N-N//3+1):
        ndp[j] = min(dp[j],ndp[j])
        ndp[j] = min(ndp[j],dp[j-1]+a+b*(j-1))
    dp = ndp
print(dp[-1])