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)