#include<bits/stdc++.h>
using namespace std;
long long cf[100000],n,m,x,y,z,a[100000],ans=0; 
int main(){
	cin>>n>>m;
	cin>>a[1];
	for(long long i=2;i<=m;i++){
		cin>>a[i];
		if(a[i]>a[i-1]){
			cf[a[i-1]]++;
			cf[a[i]]--;
		}else{
			cf[a[i-1]]--;
			cf[a[i]]++;
		}
	}
	for(long long i=1;i<n;i++){
		a[i]=a[i-1]+cf[i];
		cin>>x>>y>>z;
		ans+=min(a[i]*x,z+y*a[i]);
	} 
	cout<<ans;

	return 0;
}