G

#include <cstdio>
#include <map>
using namespace std;
typedef unsigned long long ull;
map<ull,int> mem;
unsigned dat[16][16];
unsigned sum,t;
unsigned cs[16];
ull ccs;
inline ull code()
{
    ull res=0;
    for(unsigned i=0;i<t;i++)
        res|=ull(cs[i])<<(4*i);
    return res;
}
int recurse()
{
    ull ccs=code();
    map<ull,int>::iterator it;
    if((it=mem.find(ccs))!=mem.end())return it->second;
    int res=0;
    for(int i=t-1;i>=0;i--)
        if(cs[i]!=0)
            for(int j=i-1;j>=0;j--)
                if(cs[j]!=0)
                    if(dat[i][cs[i]-1]+dat[j][cs[j]-1]==sum)
                    {
                        cs[i]--;cs[j]--;
                        res=max(res,2+recurse());
                        cs[i]++;cs[j]++;
                    }
    mem.insert(make_pair(ccs,res));
    return res;
}
int main()
{
    int n;scanf("%d%d",&n,&t);
    for(int i=0;i<t;i++)
    {
        int sz=4*n/t+(i<4*n%t?1:0);
        cs[i]=sz;
        for(int j=0;j<sz;j++)
        {
            char c;
            scanf("%d%c",&dat[i][j],&c);
        }
    }
    sum=n+1;
    printf("%d\n",recurse());
    return 0;
}