// Author -- xyr2005

#include<bits/stdc++.h>

#define lowbit(x) ((x)&(-(x)))
#define DEBUG fprintf(stderr,"Running on Line %d in Function %s\n",__LINE__,__FUNCTION__)
#define SZ(x) ((int)x.size())
#define mkpr std::make_pair
#define pb push_back

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef std::pair<int,int> pi;
typedef std::pair<ll,ll> pl;
using std::min;
using std::max;

const int inf=0x3f3f3f3f,Inf=0x7fffffff;
const ll INF=0x3f3f3f3f3f3f3f3f;

std::mt19937 rnd(std::chrono::steady_clock::now().time_since_epoch().count());
template <typename _Tp>_Tp gcd(const _Tp &a,const _Tp &b){return (!b)?a:gcd(b,a%b);}
template <typename _Tp>inline _Tp abs(const _Tp &a){return a>=0?a:-a;}
template <typename _Tp>inline void chmax(_Tp &a,const _Tp &b){(a<b)&&(a=b);}
template <typename _Tp>inline void chmin(_Tp &a,const _Tp &b){(b<a)&&(a=b);}
template <typename _Tp>inline void read(_Tp &x)
{
	char ch(getchar());bool f(false);while(!isdigit(ch)) f|=ch==45,ch=getchar();
	x=ch&15,ch=getchar();while(isdigit(ch)) x=(((x<<2)+x)<<1)+(ch&15),ch=getchar();
	f&&(x=-x);
}
template <typename _Tp,typename... Args>inline void read(_Tp &t,Args &...args){read(t);read(args...);}
inline int read_str(char *s)
{
	char ch(getchar());while(ch==' '||ch=='\r'||ch=='\n') ch=getchar();
	char *tar=s;*tar=ch,ch=getchar();while(ch!=' '&&ch!='\r'&&ch!='\n'&&ch!=EOF) *(++tar)=ch,ch=getchar();
	return tar-s+1;
}

const int N=55;
ll dp[N][N][N][2][2],f[N][2],c[N],L[N],R[N];
int main()
{
	int n,k;read(n,k);
	for(int i=1;i<=n;++i) read(L[i],R[i]);
	for(int i=0;i<k;++i) read(c[i]);
	memset(dp,63,sizeof(dp));
	for(int l=0;l<=n+1;++l) for(int a=0;a<2;++a) for(int b=0;b<2;++b) dp[k][l][l+1][a][b]=0;
	for(int i=k-1;i>=0;--i) for(int l=0;l<=n;++l)for(int a=0;a<2;++a)
	{
		memset(f,63,sizeof(f)),f[l][a]=0;
		for(int r=l+1;r<=n+1;++r)for(int b=0;b<2;++b)
		{
			for(int p=l;p<r;++p)for(int s=0;s<2;++s) chmin(dp[i][l][r][a][b],f[p][s]+dp[i+1][p][r][s][b]+((p==l?((a?R[p]:L[p])>>i&1):!s)!=((b?R[r]:L[r])>>i&1)&&p&&r!=n+1?c[i]:0));
			for(int p=l;p<r;++p)for(int s=0;s<2;++s)if(b==((b?R[r]:L[r])>>i&1)&&((L[r]^R[r])>>(i+1))) chmin(f[r][b],f[p][s]+dp[i+1][p][r][s][b]+(b==(p==l?((a?R[p]:L[p])>>i&1):!s)&&p&&r!=n+1?c[i]:0));
		}
	}
	memset(f,63,sizeof(f)),f[0][0]=f[0][1]=0;
	for(int r=1;r<=n+1;++r)for(int b=0;b<2;++b) for(int p=0;p<r;++p)for(int s=0;s<2;++s) chmin(f[r][b],f[p][s]+dp[0][p][r][s][b]);
	printf("%lld\n",f[n+1][0]);
	return 0;
}
