import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


n = int(input())
ab = [list(map(int, input().split())) for _ in range(n)]
index = list(range(n))
index.sort(key=lambda i : -ab[i][1])
inf = 10**12
dp = [inf]*(n+1)
dp[0] = 0
for ind in index:
    a,b = ab[ind]
    ndp = dp[:]
    for i in range(n):
        val = dp[i]
        if val==inf:
            continue
        ndp[i+1] = min(ndp[i+1], val+a+b*i)
    dp = ndp
#     print(dp)
v = (n//3)*2 + n%3
ans = dp[v]
print(ans)