n,m,x=map(int,input().split())
r=((m-1)//2)*((n-1)//2)*2
if x>m*n-1-r or x<m+n-2 or (x-(m+n-2))%4!=0:
  print(-1)
  exit()
ans=[]
for i in range(n):
  ans.append([])
  for j in range(m):
    if i%2 and j%2:
      ans[-1].append('#')
    else:
      ans[-1].append('.')
stock=(m*n-1-r-x)//4
count=0
for i in range(1,n,2):
  if count%2:
    for j in range(1,m,2):
      if (stock>0 and count%2) or (count%2==0 and stock<=0):
        ans[i][j-1]='#'
        stock-=1
      else:
        ans[i][j+1]='#'
  else:
    for j in range(m-2,0,-2):
      if (stock>0 and count%2) or (count%2==0 and stock<=0):
        ans[i][j+1]='#'
        stock-=1
      else:
        ans[i][j-1]='#'
  count+=1
for i in range(n):
  print(''.join(ans[i]))