import sys
input = sys.stdin.readline

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

SA=0
SB=0
ANS=0

for i in range(N-1,-1,-1):
    a,b=AB[i]

    if a*SB>b*SA:
        ANS+=a*SB
    else:
        ANS+=b*SA

    SA+=a
    SB+=b

print(ANS)