n = int(input())
mod = 2**64

res = 0
d = {}
for i in range(n):
    x,y = map(int,input().split())
    if x not in d:
        res += (i+1)*0
        d[x] = y
    else:
        res += (i+1) * d[x]
        d[x] = y

print(int(res%mod))