#define r(a,b)for(a=0;a++<h;)for(b=0;b++<w;)
char m[30][30];i,j,a,b;u[30][30];d[5]={0,1,0,-1};M=1e9;f(x,y,r,s,t){for(u[x][y]=a;r<4;)u[s=x+d[r]][t=y+d[++r]]|m[s][t]%2||f(s,t,0);}main(w,h){for(scanf("%d%d",&w,&h);gets(m[i++]););r(i,j)u[i][j]|m[i][j]%2||f(i,j,0,++a);r(i,j)r(a,b)M=u[i][j]+u[a][b]-3?M:fmin(M,fabs(i-a)+fabs(j-b)-1);printf("%d",M);}