#include<stdio.h>

 #include<string.h>

 #include<stdlib.h>

 #include<algorithm>

 #include<queue>

 //#include<iostream>

 using namespace std;

 int T,E,n;

 #define maxn 511

 struct Point{int x,f,c;}a[maxn];

 bool cmp(const Point &a,const Point &b) {return a.x<b.x;}

 #define LL long long

 #define maxm 10011

 LL f[maxm];const LL inf=1e15;

 LL que[maxm],head,tail,id[maxm];

 int main()

 {

     scanf("%d%d%d",&T,&E,&n);

     for (int i=;i<=n;i++)

         scanf("%d%d%d",&a[i].x,&a[i].f,&a[i].c);

     sort(a+,a++n,cmp);a[++n].x=E;

     for (int i=;i<=T;i++) f[i]=inf;f[]=;

     for (int i=;i<=n;i++)

     {

         head=tail=;

         for (int j=;j<=T;j++)

         {

             LL tmp=f[j]-1ll*a[i-].c*j;

             while (head<tail && que[tail-]>=tmp) tail--;

             while (head<tail && id[head]<j-a[i-].f) head++;

             que[tail]=tmp;id[tail++]=j;

             f[j]=que[head]+1ll*a[i-].c*j+1ll*j*j*(a[i].x-a[i-].x);

         }

     }

     printf("%lld\n",f[T]);

     return ;

 }