#include<bits/stdc++.h>
using namespace std;
long long cf[100001],n,m,a[100001],x,y,z,ans;
int main(){
cin>>n>>m;
cin>>a[1];
for(int 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(int 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;