#include<cstdio>

 #include<iostream>

 using namespace std;

 typedef long long LL;

 const int N = ;

 LL f[N],s[N],a[N],b[N];

 int q[N],L,R;

 inline int read() {

     int x = ,f = ;char ch = getchar();

     for (; !isdigit(ch); ch=getchar()) if(ch=='-') f=-;

     for (; isdigit(ch); ch=getchar()) x = x*+ch-'';

     return x * f;

 }

 double Slope(int i,int j) {

     return 1.0*(f[i]+s[i]-f[j]-s[j])/(1.0*(b[i]-b[j]));

 }

 int main() {

     int n = read();

     for (int i=; i<=n; ++i) a[i] = read();

     for (int i=; i<=n; ++i) {

         b[i] = read();

         s[i] = s[i-] + 1ll * b[i] * i;

         b[i] += b[i-];  // 顺序不能反！

     }

     int L = ,R = ;

     q[] = ;

     for (int i=; i<=n; ++i) {

         while (L<R && Slope(q[L],q[L+]) < (double)i) L++;

         int j = q[L];

         f[i] = f[j] + i * (b[i-] - b[j]) - (s[i-] - s[j]) + a[i];

         while (L<R && Slope(q[R-],q[R]) > Slope(q[R],i)) R--;

         q[++R] = i;

     }

     cout << f[n];

     return ;

 }