C++ :

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int maxn=2010;
int n,m;
int a[maxn],b[maxn];
int f[maxn][maxn];
int m_min(int,int,int);
void dp();
int main()
{
	//freopen("contest.in","r",stdin);
	//freopen("contest.out","w",stdout);
	dp();
	return 0;
}
int m_min(int x,int y,int z)
{
	int temp=x;
	if(temp>y) temp=y;
	if(temp>z) temp=z;
	return temp;
}
void dp()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		a[i]--;
	}
	for(int i=1;i<=m;i++)
	{
		cin>>b[i];
		b[i]--;
	}
	memset(f,0x7f,sizeof(f));
	f[n+1][m+1]=0;
	for(int i=n;i>0;i--)
		for(int j=m;j>0;j--)
			f[i][j]=m_min(f[i+1][j],f[i][j+1],f[i+1][j+1])+a[i]*b[j];
	cout<<f[1][1]<<endl;
}