from __future__ import annotations
import sys
sys.setrecursionlimit(2*10**7)
#↓codon===============================
import string
Alp_low=list(string.ascii_lowercase)
Alp_up=list(string.ascii_uppercase)
Digit="0123456789"
dij=[[0,1],[1,0],[0,-1],[-1,0]]
def nin():
    return list(map(int,input().split()))
def deq(x):
    return [i-1 for i in x]
mod=998244353
_factorial=[1]
def factorial(n):
    while len(_factorial)<=n:
        _factorial.append((_factorial[-1]*len(_factorial))%mod)
    return _factorial[n]

_inv_factorial=[1]
def inv_factorial(n):
    while len(_inv_factorial)<=n:
        _inv_factorial.append((_inv_factorial[-1]*pow(len(_inv_factorial),mod-2,mod))%mod)
    return _inv_factorial[n]

def binom(n,r):
    if r>=mod:
        raise ValueError("r is too big")
    if n<0:
        return 0
    if r>n:
        return 0
    if r<0:
        return 0
    ans=((factorial(n)*inv_factorial(r))%mod*inv_factorial(n-r))%mod
    return ans

def main():
    h,w,k=nin()
    if k==0:
        for _ in range(h):
            print("#"*w)
        return
    def calc1(h,w,k):
        if not 2<=k<=h+w-2:
            return False,[[]]
        if k<=w:
            ans=[[] for _ in range(h)]
            for i in range(h):
                if i==0:
                    for j in range(k-1):
                        ans[i].append(".")
                    for j in range(w-(k-1)):
                        ans[i].append("#")
                    continue
                for j in range(w):
                    ans[i].append("#")
            return True,ans
        else:
            ans=[[] for _ in range(h)]
            for i in range(h):
                if i==0:
                    for j in range(w):
                        ans[i].append(".")
                    continue
                for j in range(w):
                    if j==0 and i<=k-w+1:
                        ans[i].append(".")
                    else:
                        ans[i].append("#")
            return True,ans

    def calc2(h,w,k):
        if k<h:
            return False,[[]]
        ans=[["#"]*w for _ in range(h)]
        for i in range(h):
            ans[i][0]="."
        rem=k-h
        for i in range(0,h,2)[::-1]:
            for j in range(1,w-1):
                if i in [0,h-1]:
                    x=1
                else:
                    x=2
                if rem-x>=0:
                    ans[i][j]="."
                    rem-=x
        if rem!=0:
            return False,[[]]
        else:
            return True,ans

    def calc3(h,w,k):
        fl,ans=calc2(w,h,k)
        if fl==False:
            return fl,ans
        new=[[ans[j][i] for j in range(w)] for i in range(h)]
        return fl,new


    fl,ans=calc1(h,w,k)
    if fl:
        for i in ans:
            print("".join(i))
        return
    fl,ans=calc3(h,w,k)
    if fl:
        for i in ans:
            print("".join(i))
        return
    fl,ans=calc2(h,w,k)
    if fl:
        for i in ans:
            print("".join(i))
        return
        

    print(-1)

if __name__=="__main__":
    main()