h,w,x = map(int,input().split())
a,b = h//2+1,w//2+1
L = a+b-2
if a%2==0 and b%2==0:
    R = a*b-2
else:
    R = a*b-1
if x%2:
    print(-1)
    exit()
x //= 2
#print(a,b,L,x,R)
if x%2 != L%2 or not (L <= x <= R):
    print(-1)
    exit()

ans = [[0]*w for _ in range(h)]


def dist(i,j): return a+b-i-j-2
res = []
p,q,cnt = 0,0,0

if a%2:
    for i in range(h):
        for j in range(w):
            if i%2==0: ans[i][j] = 1

    while cnt + dist(p,q) != x:
        if p%2==0:
            if q != b-1: q += 1
            else:
                ans[2*p+1][2*q] = 1
                p += 1
                
        else:
            if q: q -= 1
            else:
                ans[2*p+1][2*q] = 1
                p += 1
        cnt += 1

    while p != a-1:
        ans[2*p+1][2*q] = 1
        p += 1

elif b%2:
    for i in range(h):
        for j in range(w):
            if j%2==0: ans[i][j] = 1

    while cnt + dist(p,q) != x:
        if q%2==0:
            if p != a-1: p += 1
            else:
                ans[2*p][2*q+1] = 1
                q += 1
                
        else:
            if p: p -= 1
            else:
                ans[2*p][2*q+1] = 1
                q += 1
        cnt += 1

    while q != b-1:
        ans[2*p][2*q+1] = 1
        q += 1

else:#ぐぐ
    while cnt + dist(p,q) != x:
        if p%2==0:
            if q != b-1: q += 1
            else:
                ans[2*p+1][2*q] = 1
                p += 1
                
        else:
            if q: q -= 1
            else:
                ans[2*p+1][2*q] = 1
                p += 1
        cnt += 1
        if p == a-2 and q == 0: break
    #print(p,q)
    if p != a-2 or q != 0:
        for i in range(h):
            for j in range(w):
                if i%2==0: ans[i][j] = 1
        while p != a-1:
            ans[2*p+1][2*q] = 1
            p += 1
    else:
        for i in range(h-3):
            for j in range(w):
                if i%2==0: ans[i][j] = 1
        for i in range(h-3,h):
            for j in range(w):
                if j%2==0: ans[i][j] = 1
        while cnt + dist(p,q) != x:
            #print(p,q)
            if q%2==0:
                if p != a-1: p += 1
                else:
                    ans[2*p][2*q+1] = 1
                    q += 1
                    
            else:
                if p != a-2: p -= 1
                else:
                    ans[2*p][2*q+1] = 1
                    q += 1
            cnt += 1
        #print(p,q,b-1)
        while q != b-1:
            ans[2*p][2*q+1] = 1
            q += 1
        
        





s = "#."
for ai in ans:
    print("".join(map(lambda i:s[i],ai)))