N=int(input())
P=[list(map(int,input().split())) for i in range(N)]

P.sort(key=lambda x:x[0])
P.sort(key=lambda x:x[1],reverse=True)

DP=[P[i][0] for i in range(N)]
for i in range(1,N):
    if DP[i]>DP[i-1]:
        DP[i]=DP[i-1]

#print(DP)

if N%3==0:
    days=N*2//3
elif N%3==1:
    days=(N-1)*2//3+1
else:
    days=(N+1)*2//3


for i in range(1,days):
    NDP=[10**15]*N
    for j in range(1,N):
        NDP[j]=min(DP[j-1]+(P[j][0]+P[j][1]*i),NDP[j-1])
        #print(DP[j-1]+(P[j][0]+P[j][1]*i),NDP[j-1])

    DP=NDP

    #print(DP)

print(min(DP))