#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
template<class S, class T> inline S min_L(S a,T b){
  return a<=b?a:b;
}
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(const char c[]){
  int i=0;
  for(i=0;c[i]!='\0';i++){
    my_putchar_unlocked(c[i]);
  }
}
int X;
int Y;
int K;
int xx;
int yy;
int r;
int k;
char res[1000][1002];
int main(){
  int i;
  rd(X);
  rd(Y);
  rd(K);
  for(i=(0);i<(X);i++){
    int j;
    for(j=(0);j<(Y);j++){
      res[i][j] = '.';
    }
  }
  for(i=(1);i<(X);i+=(2)){
    int j;
    for(j=(1);j<(Y);j+=(2)){
      res[i][j] = '#';
    }
  }
  if(K%2){
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  auto WYIGIcGE = (((X)+ 1) / 2);
  auto t_ynMSdg = (((Y)+ 1) / 2);
  xx=WYIGIcGE;
  yy=t_ynMSdg;
  r = K / 2 - (xx - 1) - (yy - 1);
  if(r%2){
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  r /= 2;
  if((xx-1)/2 * (yy-1) >= r){
    for(i=(1);i<(X);i+=(2)){
      int j;
      for(j=(0);j<(Y-2);j+=(2)){
        res[i][j] = '#';
      }
    }
    for(i=(1);i<(xx);i+=(2)){
      res[2*i+1][Y-1] = '#';
      k =min_L(r, yy-1);
      res[2*i+1][Y-1-k*2] = '.';
      r -= k;
    }
  }
  else if((yy-1)/2 * (xx-1) >= r){
    for(i=(1);i<(Y);i+=(2)){
      int j;
      for(j=(0);j<(X-2);j+=(2)){
        res[j][i] = '#';
      }
    }
    for(i=(1);i<(yy);i+=(2)){
      res[X-1][2*i+1] = '#';
      k =min_L(r, xx-1);
      res[X-1-k*2][2*i+1] = '.';
      r -= k;
    }
  }
  else{
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  {
    int jPV_0s1p;
    for(jPV_0s1p=(0);jPV_0s1p<(X);jPV_0s1p++){
      wt_L(res[jPV_0s1p]);
      wt_L('\n');
    }
  }
  return 0;
}
// cLay version 20210227-1

// --- original code ---
// int X, Y, K, xx, yy, r, k;
// char res[1000][1002];
// {
//   rd(X,Y,K);
//   rep(i,X) rep(j,Y) res[i][j] = '.';
//   rep(i,1,X,2) rep(j,1,Y,2) res[i][j] = '#';
// 
//   if(K%2) wt(-1), return 0;
//   (xx, yy) = ((X,Y) + 1) / 2;
//   r = K / 2 - (xx - 1) - (yy - 1);
// 
//   if(r%2) wt(-1), return 0;
//   r /= 2;
// 
//   if((xx-1)/2 * (yy-1) >= r){
//     rep(i,1,X,2) rep(j,0,Y-2,2) res[i][j] = '#';
//     rep(i,1,xx,2){
//       res[2*i+1][Y-1] = '#';
//       k = min(r, yy-1);
//       res[2*i+1][Y-1-k*2] = '.';
//       r -= k;
//     }
//   } else if((yy-1)/2 * (xx-1) >= r){
//     rep(i,1,Y,2) rep(j,0,X-2,2) res[j][i] = '#';
//     rep(i,1,yy,2){
//       res[X-1][2*i+1] = '#';
//       k = min(r, xx-1);
//       res[X-1-k*2][2*i+1] = '.';
//       r -= k;
//     }
//   } else {
//     wt(-1);
//     return 0;
//   }
// 
//   wtLn(res(X));
// }