#include<bits/stdc++.h>
using namespace std;
int n,m,k[1050000],pre[1050000],x[1050000];
int vis[1050000],col[1050000],cnt[2];
int dp[1050000],sum;
vector<int> edge[1050000];
queue<int> qu;
bitset<1005000> f;
void dfs(int x) {
    vis[x]=1;
    cnt[col[x]]++;
    for (auto y:edge[x]) {
        if (vis[y]) continue;
        col[y]=col[x]^1;
        dfs(y);
    }
}
int main() {
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++) {
        scanf("%d",&k[i]);
        pre[i]=pre[i-1]+k[i];
        for (int j=pre[i-1]+1;j<=pre[i];j++) {
            scanf("%d",&x[j]);
            if (j!=pre[i-1]+1) {
                edge[x[j-1]].push_back(x[j]);
                edge[x[j]].push_back(x[j-1]);
            }
        }
    }
    for (int i=1;i<=n;i++) {
        if (vis[i]==0) {
            dfs(i);
            if (cnt[0]>cnt[1]) dp[cnt[0]-cnt[1]]++;
            if (cnt[1]>cnt[0]) dp[cnt[1]-cnt[0]]++;
            cnt[0]=cnt[1]=0;
        }
    }
    for (int i=1;i<=n;i++) {
        for (auto j:edge[i]) {
            if (col[i]==col[j]) {
                printf("impossible\n");
                return 0;
            }
        }
    }
    for (int i=1;i<=n;i++) {
        if (dp[i]>=3) {
            dp[i*2]+=(dp[i]-1)/2;
            dp[i]-=(dp[i]-1)/2*2;
        }
    }
    for (int i=1;i<=n;i++) sum+=dp[i]*i;
    f[0]=1;
    for (int i=1;i<=sum/2;i++) {
        for (int j=0;j<dp[i];j++) {
            f|=(f<<(i*2));
        }
    }
    for (int i=sum;i>=0;i--) {
        if (f[i]) {
            printf("%d\n",sum-i);
            return 0;
        }
    }
    printf("%d\n",sum);
    return 0;
}