#include <iostream>

int main(int argc, char** argv)
{
	int **map,sizeX,sizeY,max,current;
	int step,mainD,k;
	bool **used;
	scanf("%d %d",&sizeY,&sizeX);
	while (sizeX && sizeY){
		max=1;
		map=new int*[sizeY];
		used=new bool*[sizeY];
		for (int i=0;i<sizeY;i++){
			map[i] = new int[sizeX];
			used[i] = new bool[sizeX];
			for (int j=0;j<sizeX;j++){
				scanf("%d",&map[i][j]);
				used[i][j]=false;
			}
		}
		for (int i=0; i<sizeY; i++){
			for (int j=0;j<sizeX;j++){
				if (!used[i][j]){
					used[i][j]=true;
					current=0;
					if (j<sizeX-1 && i<sizeY-1){
						if (map[i][j]==map[i][j+1] && map[i+1][j]==map[i+1][j+1]){ //vertical
							current=1;
							step=map[i+1][j]-map[i][j];
							while(i+current<sizeY && j+current<sizeX){
								for (k=0;k<=current;k++) //JDEME DOLU
									if (map[i+current][j+k]+step!=map[i+current+1][j+k])
										break;
								if (k==current+1){
									for (k=0;k<=current+1;k++) //JDEME VLEVO
										if (map[i+k][j+current]!=map[i+k][j+current+1])
											break;												
									if (k!=current+2) break;
								}
								else break;
								current++;
							}
						}
						else if (map[i][j]==map[i+1][j] && map[i][j+1]==map[i+1][j+1]){ //horizontal
							current=1;
							step=map[i][j+1]-map[i][j];
							while(i+current+1<sizeY && j+current+1<sizeX){
								for (k=0;k<=current;k++) //JDEME VLEVO
									if (map[i+k][j+current]+step!=map[i+k][j+current+1])
										break;
								if (k==current+1){
									for (k=0;k<=current+1;k++) //JDEME DOLU
										if (map[i+current][j+k]!=map[i+current+1][j+k])
											break;
									if (k!=current+2) break;
								}
								else break;
								current++;
							}
						}
						else if ((map[i][j]==map[i+1][j+1] && map[i][j+1]+map[i+1][j]==2*map[i][j])   //hlavni
							||   (map[i+1][j]==map[i][j+1] && map[i][j]+map[i+1][j+1]==2*map[i+1][j]) //vedlejsi
							){ // diagonal
							current=1;
							step=map[i+1][j]-map[i][j];
							mainD=(map[i][j]==map[i+1][j+1]) ? -1 : 1;
							while(i+current+1<sizeY && j+current+1<sizeX){
								for (k=0;k<=current;k++) //JDEME VLEVO
									if (map[i+k][j+current]+(step*mainD)!=map[i+k][j+current+1])
										break;
								if (k==current+1){
									for (k=0;k<=current+1;k++) //JDEME DOLU
										if (map[i+current][j+k]+step!=map[i+current+1][j+k])
											break;
									if (k!=current+2) break;
								}
								else break;
								current++;
							}
						}
						if ((current+1)*(current+1)>max) max=(current+1)*(current+1);
					}
				}
			}
			delete [] map[i];
			delete [] used[i];
		}
		delete [] map;
		delete [] used;
		printf("%d\n",max);
		scanf("%d %d",&sizeY,&sizeX);
	}
	return 0;
}