n=int(input())
c=[tuple(map(int,input().split())) for i in range(n)]
c.sort(key=lambda p:-p[1])
X=10**20
q=[X]*(((n+2)//3)*2-(n%3==1)+1)
q[0]=0
for a,b in c:
  for i in reversed(range(len(q)-1)):
    q[i+1]=min(q[i+1],q[i]+a+b*i)
print(q[-1])