n=int(input())
a,b=[0]*n,[0]*n
for i in range(n):
  a[i],b[i]=map(int,input().split())

cuma=[0]*(n+1)
cumb=[0]*(n+1)
for i in range(n-1,-1,-1):
  cuma[i]=cuma[i+1]+a[i]
  cumb[i]=cumb[i+1]+b[i]

row=[-1]*n
L,R=0,n-1
for i in range(n):
  if a[i]*cumb[i+1]<b[i]*cuma[i+1]:
    row[L]=i
    L+=1
  else:
    row[R]=i
    R-=1

ans=0
tmp=0
for i in row:
  ans+=tmp*a[i]
  tmp+=b[i]

print(ans)