n = int(input())
# 用字典定义一个哈希表
dic = {}
sum =0
for i in range(n):
    x,y = map(int,input().split())
    if x not in dic:
        dic[x]=y
    else:
        sum +=dic[x]*(i+1)
        dic[x]=y
print(sum& ((1 << 64) - 1))