#![allow(non_snake_case,dead_code,unused_imports)]
use proconio::{*,marker::*};



fn main(){
    input!{
        h:usize,
        w:usize,
        k:usize,
    }
    
    let mut ans=vec![vec![0;w];h];
    let out=|ans:&Vec<Vec<usize>>|{
        for i in 0..h{
            for j in 0..w{
                if ans[i][j]==1{
                    print!("#");
                } else{
                    print!(".");
                }
            }
            println!();
        }
    };
    
    if h==1 || w==1{
        if k>1{
            println!("-1");
            return;
        }
        
        if k==1{
            ans[0][0]=1;
        }
        out(&ans);
        return;
    }
    if k==0{
        out(&ans);
        return;
    }
    if k==1{
        println!("-1");
        return;
    }
    if k==2{
        ans[0][0]=1;
        out(&ans);
        return;
    }
    
    let mut ps=vec![];
    ps.push(P::new(0,1));
    
    for j in (1..w).step_by(4){
        if j+2==w-1{
            for i in (1..h-1).step_by(4){
                ps.push(P::new(i,j));
                ps.push(P::new(i,j+1));
                if i+1==h-1{
                    break;
                }
                ps.push(P::new(i+1,j+1));
                if i+2==h-1{
                    break;
                }
                ps.push(P::new(i+2,j+1));
                ps.push(P::new(i+2,j));
                if i+3==h-1{
                    break;
                }
                ps.push(P::new(i+3,j));
            }
            break;
        }
        
        for i in 1..h-1{
            ps.push(P::new(i,j));
        }
        if j+1==w-1{
            break;
        }
        ps.push(P::new(h-2,j+1));
        
        if j+4==w-1{
            for i in (1..h-1).rev().step_by(4){
                ps.push(P::new(i,j+2));
                ps.push(P::new(i,j+2+1));
                if i-1==0{
                    break;
                }
                ps.push(P::new(i-1,j+2+1));
                if i-2==0{
                    break;
                }
                ps.push(P::new(i-2,j+2+1));
                ps.push(P::new(i-2,j+2));
                if i-3==0{
                    break;
                }
                ps.push(P::new(i-3,j+2));
            }
            break;
        }
        for i in (1..h-1).rev(){
            ps.push(P::new(i,j+2));
        }
        if j+3==w-1{
            break;
        }
        ps.push(P::new(1,j+3));
    }
    
    let mut d=vec![vec![!0;w];h];
    for (i,&p) in ps.iter().enumerate(){
        d[p]=i;
    }
    
    if k%2==0{
        assert!(k>=2);
        ps.remove(0);
        let nes=(k-2)/2;
        if ps.len()<nes{
            println!("-1");
            return;
        }
        
        for &p in ps.iter().take(nes){
            ans[p]=1;
        }
    } else{
        assert!(k>=3);
        let nes=(k-1)/2;
        if ps.len()<nes{
            println!("-1");
            return;
        }
        
        for &p in ps.iter().take(nes){
            ans[p]=1;
        }
    }
    
    out(&ans);
}



use itertools::*;



trait ChangeMinMax:Copy+PartialOrd{
    fn chmin(&mut self,a:Self)->bool{
        *self>a && {
            *self=a;
            true
        }
    }
    
    fn chmax(&mut self,a:Self)->bool{
        *self<a && {
            *self=a;
            true
        }
    }
}

impl<T:Copy+PartialOrd> ChangeMinMax for T{}



// library: https://github.com/rhoo19937/cp-lib



// LURD
const DD:[P;4]=[P{i:0,j:!0},P{i:!0,j:0},P{i:0,j:1},P{i:1,j:0}];
const DX:[P;8]=[P{i:0,j:!0},P{i:!0,j:!0},P{i:!0,j:0},P{i:!0,j:1},P{i:0,j:1},P{i:1,j:1},P{i:1,j:0},P{i:1,j:!0}];

#[derive(Clone,Copy,PartialEq,Eq,PartialOrd,Ord,Hash,Default)]
struct P{
    i:usize,
    j:usize,
}
impl P{
    fn new(i:usize,j:usize)->P{
        P{i,j}
    }
    
    fn in_range(self,h:usize,w:usize)->bool{
        self.i<h && self.j<w
    }
    
    fn id(self,w:usize)->usize{
        self.i*w+self.j
    }
    
    fn from(id:usize,w:usize)->P{
        P::new(id/w,id%w)
    }
    
    fn manh(self,p:P)->usize{
        let abs_diff=|a,b|(a as i64-b as i64).abs() as usize;
        abs_diff(self.i,p.i)+abs_diff(self.j,p.j)
    }
    
    fn parity(self)->bool{
        (self.i^self.j)%2==1
    }
    
    fn dir(self,p:P)->usize{
        if self.i==p.i{
            if self.j-1==p.j{
                0
            } else{
                assert!(self.j+1==p.j);
                2
            }
        } else{
            if self.i-1==p.i{
                1
            } else{
                assert!(self.i+1==p.i);
                3
            }
        }
    }
}
impl std::fmt::Debug for P{
    fn fmt(&self,f:&mut std::fmt::Formatter)->std::fmt::Result{
        write!(f,"({}, {})",self.i,self.j)
    }
}
impl std::ops::Add for P{
    type Output=P;
    fn add(self,a:P)->P{
        P{
            i:self.i+a.i,
            j:self.j+a.j,
        }
    }
}
impl std::ops::Sub for P{
    type Output=P;
    fn sub(self,a:P)->P{
        P{
            i:self.i-a.i,
            j:self.j-a.j,
        }
    }
}
impl std::ops::Mul<usize> for P{
    type Output=P;
    fn mul(self,a:usize)->P{
        P{
            i:self.i*a,
            j:self.j*a,
        }
    }
}
impl std::ops::Div<usize> for P{
    type Output=P;
    fn div(self,a:usize)->P{
        P{
            i:self.i/a,
            j:self.j/a,
        }
    }
}
impl std::ops::Neg for P{
    type Output=P;
    fn neg(self)->P{
        P{
            i:self.i.wrapping_neg(),
            j:self.j.wrapping_neg(),
        }
    }
}


macro_rules! impl_p_ops{
    ($t:ty,$assign_trait:ident,$assign_func:ident,$op:tt)=>{
        impl std::ops::$assign_trait<$t> for P{
            fn $assign_func(&mut self,a:$t){
                *self=*self $ op a;
            }
        }
    }
}
impl_p_ops!(P,AddAssign,add_assign,+);
impl_p_ops!(P,SubAssign,sub_assign,-);
impl_p_ops!(usize,MulAssign,mul_assign,*);
impl_p_ops!(usize,DivAssign,div_assign,/);


macro_rules! impl_p_index{
    ($t:ty)=>{
        impl<T:std::ops::Index<usize>> std::ops::Index<P> for $t{
            type Output=T::Output;
            fn index(&self,idx:P)->&T::Output{
                &self[idx.i][idx.j]
            }
        }
        impl<T:std::ops::IndexMut<usize>> std::ops::IndexMut<P> for $t{
            fn index_mut(&mut self,idx:P)->&mut T::Output{
                &mut self[idx.i][idx.j]
            }
        }
    }
}
impl_p_index!([T]);
impl_p_index!(Vec<T>);


fn iterp(h:usize,w:usize)->impl Iterator<Item=P>{
    (0..h).map(move|i|(0..w).map(move|j|P::new(i,j))).flatten()
}



#[cfg(feature="local")]
include!(concat!(env!("HOME"), "/cp/lib/debug_mod.rs"));
#[cfg(not(feature="local"))]
#[macro_export]macro_rules! debug{($($t:tt)*)=>{}}