#include<bits/stdc++.h>
#define Yukinoshita namespace
#define Yukino std
using Yukinoshita Yukino;
int read()
{
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9') w=ch=='-'?-1:1,ch=getchar();
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
vector<pair<int,int>> qwq;
int n,m;
char mp[105][105];
void dfs(int x,int y,int c)
{
	int i,j;
	if(x==n+1)
	{
		for(i=1;i<=n;i++,puts(""))
			for(j=1;j<=m;j++)
				putchar(mp[i][j]);
		exit(0);
	}
	int nx=y==m?x+1:x,ny=y==m?1:y+1;
	if(mp[x][y]) dfs(nx,ny,c);
	else
	{
		for(auto p:qwq)
			if(x+p.first-1<=n&&y+p.second-1<=m)
			{
				for(i=x;i<x+p.first;i++)
					for(j=y;j<y+p.second;j++)
						if(mp[i][j])
							goto bre;
				for(i=x;i<x+p.first;i++)
					for(j=y;j<y+p.second;j++)
						mp[i][j]=c+'A';
				dfs(nx,ny,c+1);
				for(i=x;i<x+p.first;i++)
					for(j=y;j<y+p.second;j++)
						mp[i][j]=0;
				bre:;
			}
	}
}
int main()
{
	n=read(),m=read();
	int c=read();
	if(n*m%c)
	{
		cout<<"impossible";
		return 0;
	}	
	int x=n*m/c,i;
	for(i=1;i<=x;i++)
		if(x%i==0)
			qwq.push_back({i,x/i});
	random_shuffle(qwq.begin(),qwq.end());
	dfs(1,1,0);
	cout<<"impossible";
}