#include <bits/stdc++.h>
using namespace std;
long long n,arr[2000000],sum[2000000],maxx=-1,k,m,ans,cha[2000000],a[2000000],b[2000000],c[2000000];
int main(){
   ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m>>arr[0];
	for(int i=1;i<m;i++){
		cin>>arr[i];
		cha[min(arr[i],arr[i-1])]++;
		cha[max(arr[i],arr[i-1])]--;
	}
	for(int i=1;i<n;i++){
		sum[i]=sum[i-1]+cha[i];
	}
	for(int i=1;i<n;i++){
		cin>>a[i]>>b[i]>>c[i];
		ans+=min(sum[i]*a[i],sum[i]*b[i]+c[i]);
	}
	cout<<ans;
	return 0;
}

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

OSAxMAozIDEgNCAxIDUgOSAyIDYgNSAzCjIwMCAxMDAgNTAKMzAwIDI5OSAxMDAKNTAwIDIwMCA1MDAKMzQ1IDIzNCAxMjMKMTAwIDUwIDEwMAo2MDAgMTAwIDEKNDUwIDQwMCA4MAoyIDEgMTA=

9 10
3 1 4 1 5 9 2 6 5 3
200 100 50
300 299 100
500 200 500
345 234 123
100 50 100
600 100 1
450 400 80
2 1 10