#include <bits/stdc++.h>   using namespace std;   const int maxn = 1e5 + 5;   long long a[maxn], b[maxn], dp[maxn];   int q[maxn];   int head = 0, tail = 0;   double A(int i, int j) { return dp[i] - dp[j]; }   double B(int i, int j) { return b[i] - b[j]; }   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int n;     cin >> n;     for (int i = 1; i <= n; i++) cin >> a[i];     for (int i = 1; i <= n; i++) cin >> b[i];     dp[1] = 0;     int head = 1, tail = 1;     q[tail] = 1;     for (int i = 2; i <= n; i++) {       while (head < tail &&              A(q[head + 1], q[head]) / B(q[head + 1], q[head]) >= -a[i])         head++;       dp[i] = dp[q[head]] + b[q[head]] * a[i];       while (head < tail && A(i, q[tail]) / B(i, q[tail]) >=                                 A(q[tail], q[tail - 1]) / B(q[tail], q[tail - 1]))         tail--;       q[++tail] = i;     }     cout << dp[n] <<   n ;     return 0;   }   