#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
typedef long long llong;
const int MAXN = 100000 + 10;
const llong INF = 1e18;
const int INTINF = 1e9;
int n, m;
int a[MAXN];
int b[MAXN];
llong dp[MAXN];
void solve()
{
dp[m] = 0;
for (int i = m - 1 ; i >= 1 ; --i)
{
dp[i] = dp[i + 1] + a[n];
}
for (int i = n - 1 ; i >= 1 ; --i)
{
for (int j = m ; j >= 1 ; --j)
{
dp[j] += b[j];
}
for (int j = m - 1 ; j >= 1 ; --j)
{
dp[j] = std::min(dp[j], dp[j + 1] + a[i]);
}
}
std::cout << dp[1] << '\n';
}
void input()
{
std::cin >> n >> m;
for (int i = 1 ; i <= n ; ++i)
{
std::cin >> a[i];
}
for (int i = 1 ; i <= m ; ++i)
{
std::cin >> b[i];
}
}
void fastIOI()
{
std::ios_base :: sync_with_stdio(0);
std::cout.tie(nullptr);
std::cin.tie(nullptr);
}
int main()
{
fastIOI();
input();
solve();
return 0;
}
