#include <iostream>
#include <algorithm>

using namespace std;

const int MAX_WIDTH = 20;
const int MAX_HEIGHT = 20;
const int MAX_PIECES = 20;
const int INFINITY = 1000000;

int largestArea[MAX_WIDTH+1][MAX_HEIGHT+1][MAX_PIECES+1];

int main (){
  
  // initialization
  for (int w = 1; w <= MAX_WIDTH; w++){
    for (int h = 1; h <= MAX_HEIGHT; h++){
      largestArea[w][h][1] = w*h;
    }
  }
  
  // dynamic programming
  for (int m = 2; m <= MAX_PIECES; m++){
    
    // build each piece using smaller pieces
    for (int w = 1; w <= MAX_WIDTH; w++){
      for (int h = 1; h <= MAX_HEIGHT; h++){
	largestArea[w][h][m] = INFINITY;
	
	for (int m1 = 1; m1 < m; m1++){
	  
	  // try all vertical cuts
	  for (int w1 = 1; w1 < w; w1++){
	    largestArea[w][h][m] = min (largestArea[w][h][m],
					max (largestArea[w1][h][m1],
					     largestArea[w-w1][h][m-m1]));
	  }
	  
	  // try all horizontal cuts
	  for (int h1 = 1; h1 < h; h1++){
	    largestArea[w][h][m] = min (largestArea[w][h][m],
					max (largestArea[w][h1][m1],
					     largestArea[w][h-h1][m-m1]));
	  }	  
	}
      }
    }
  }
  
  while (true){
    int width, height, numPieces;
    cin >> width >> height >> numPieces;
    if (width == 0 && height == 0 && numPieces == 0) break;
    cout << largestArea[width][height][numPieces] << endl;
  }
  
  return 0;
}