1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<iostream>
 6 #include<algorithm>
 7 #include<queue>
 8 using namespace std;
 9
10 typedef long long LL;
11 const int N=50010;
12 int n,pl,Q[N];
13 LL l=0,r=0,ai,xj,bj,j,f[N];
14 struct node{
15     LL a,b;
16     bool bk;
17 }p[N];
18
19 // f[i]=f[j]+a[j+1]*b[i]
20 // ai=b[i]
21 // xj=a[j+1]
22 // bj=f[j]
23
24 LL XX(int i,int j){return p[i+1].a-p[j+1].a;}
25 LL YY(int i,int j){return f[i]-f[j];}
26 double X(int i){return p[i+1].a;}
27 double Y(int i){return f[i];}
28 double find_k(int i,int j){return (Y(i)-Y(j))/(X(i)-X(j));}
29
30 bool cmp(node x,node y){
31     if(x.a!=y.a) return x.a>y.a;
32     return x.b>y.b;
33 }
34
35 bool judge_1()
36 {
37     LL tx=XX(Q[l],Q[l+1]),ty=YY(Q[l],Q[l+1]);
38     if(tx>=0) return ty>=((-ai)*tx);
39     return ty<=((-ai)*tx);
40 }
41
42 bool judge_2(int i)
43 {
44     LL t0=YY(Q[r],Q[r-1]),t1=XX(Q[r],Q[r-1]),t2=YY(i,Q[r]),t3=XX(i,Q[r]);
45     if(t1<0) t0=-t0,t1=-t1;
46     if(t3<0) t2=-t2,t3=-t3;
47     return (t0*t3)<(t1*t2);
48 }
49
50 int main()
51 {
52     freopen("a.in","r",stdin);
53     // freopen("acquire.in","r",stdin);
54     // freopen("acquire.out","w",stdout);
55     scanf("%d",&n);
56     for(int i=1;i<=n;i++)
57     {
58         scanf("%lld%lld",&p[i].a,&p[i].b);
59         p[i].bk=1;
60     }
61     sort(p+1,p+1+n,cmp);
62     j=1;
63     for(int i=2;i<=n;i++)
64     {
65         if(p[i].a<=p[j].a && p[i].b<=p[j].b) p[i].bk=0;
66         else j=i;
67     }
68     pl=1;
69     for(int i=2;i<=n;i++)
70         if(p[i].bk) p[++pl]=p[i];
71
72     for(int i=1;i<=pl;i++)
73     {
74         ai=p[i].b;
75         while(l<r && judge_1()) l++;/*find_k(Q[l],Q[l+1])>=(-ai)*/
76         j=Q[l];
77         xj=p[j+1].a;
78         bj=f[j];
79         f[i]=ai*xj+bj;
80         while(l<r && judge_2(i)) r--;/*find_k(Q[r],Q[r-1])<find_k(i,Q[r])*/
81         Q[++r]=i;
82     }
83     printf("%lld\n",f[pl]);
84     return 0;
85 }