import sys
input = sys.stdin.readline

H,W,X=map(int,input().split())

ANS=[["."]*W for i in range(H)]
k=H-1+W-1
if X<k or (X-k)%4!=0:
    print(-1)
    exit()



for i in range(H):
    for j in range(W):
        if i%2==1 and j%2==1:
            ANS[i][j]="#"

for i in range(H):
    ANS[i][0]=0

for j in range(W):
    ANS[-1][j]=0

NOWX=1
NOWY=0
while k<X:
    if NOWX+2<H and NOWY+1<W:
        k+=4
        ANS[NOWX][NOWY]="."
        for i,j in [(NOWX-1,NOWY+1),(NOWX-1,NOWY+2),(NOWX,NOWY+2),(NOWX+1,NOWY+1),(NOWX+1,NOWY+2)]:
                    ANS[i][j]=0
        NOWY+=2


    elif NOWY+1==W:
        NOWX+=4
        NOWY=0

    else:
        break

if k<X and H%4==3:
    NOWX=H-1
    NOWY=3
    while k<X:
        if NOWY+1<W:
            k+=4
            ANS[NOWX][NOWY]="."
            for i,j in [(NOWX-1,NOWY-1),(NOWX-1,NOWY+1),(NOWX-2,NOWY-1),(NOWX-2,NOWY),(NOWX-2,NOWY+1)]:
                        ANS[i][j]=0
            NOWY+=4
        else:
            break

if k!=X:
    print(-1)
    exit()

for i in range(H):
    for j in range(W):
        if ANS[i][j]==".":
            flag=0
            for z,w in [(i-1,j),(i+1,j),(i,j-1),(i,j+1)]:
                if 0<=z<H and 0<=w<W and ANS[z][w]==0:
                    ANS[i][j]="#"


for j in range(W):
    if j%2==0 and ANS[H-3][j]==".":
        ANS[H-2][j]="."

for j in range(W):
    for i in range(H-2,-1,-1):
        if ANS[i][j]=="." and ANS[i+1][j]=="#":
            ANS[i][j]="#"

for i in range(H):
    for j in range(W):
        if ANS[i][j]==0:
            ANS[i][j]="."

for ans in ANS:
    print("".join(ans))