from sys import stdin,stdout
input=stdin.readline

def main():
    N,M = list(map(int, input().split()))
    if M>N:
        print(-1)
        return
    graph={}
    for i in range(M):
        u,v = list(map(int, input().split()))
        try: graph[u].add(v)
        except: graph[u]={v}
        try: graph[v].add(u)
        except: graph[v]={u}
    if len(graph)<N:
        print(-1)
        return
    deg={}
    for key in graph:
        try: deg[len(graph[key])].add(key)
        except: deg[len(graph[key])]={key}
    #print(deg)
    #print(graph)
    # deg2 -> 1...1000
    # deg1 -> 1001...2000
    deg1,deg2=2000,1000
    inf=10**8
    matrix=[list(range(inf-i*1001-N-1,inf-i*1001)) for i in range(0,N+1)]
    #print(matrix)
    while deg[1]:
        v=deg[1].pop()
        u=graph.pop(v).pop()
        #print(v,u)
        matrix[u][v]=deg1
        matrix[v][u]=deg1
        deg1-=1
        if u in deg[1]:
            deg[1].remove(u)
            graph.pop(u)
        else:
            graph[u].remove(v)
            try: deg[len(graph[u])].add(u)
            except: deg[len(graph[u])]={u}
            if len(deg[len(graph[u])+1])==1:
                deg.pop(len(graph[u])+1)
            else:
                deg[len(graph[u])+1].remove(u)
            if len(graph[u])==1:
                deg[1].add(u)
    if 1 in deg:
        deg.pop(1)
    if len(deg)==0:
        for i in range(1,N):
            #print(*matrix[i][i+1:])
            for j in range(i+1,N+1):
                stdout.write(str(matrix[i][j])+' ')
            stdout.write('\n')
        return
    elif len(deg)>1 or 2 not in deg:
        print(-1)
        return
    #print(deg)
    #print(graph)
    while deg[2]:
        v=deg[2].pop()
        cur=[v]
        while cur[-1] in graph:
            szomsz=graph.pop(cur[-1])
            for u in szomsz:
                if u in deg[2]:
                    deg[2].remove(u)
                    cur.append(u)
                    break
        #print(cur)
        for i in range(len(cur)):
            u=cur[i]
            v=cur[i-1]
            matrix[u][v]=deg2
            matrix[v][u]=deg2
            deg2-=1
                
    #print(N,len(matrix),len(matrix[0]))
    for i in range(1,N):
        #print(*matrix[i][i+1:])
        for j in range(i+1,N+1):
            stdout.write(str(matrix[i][j])+' ')
        stdout.write('\n')
main()