// original:
// https://yukicoder.me/submissions/8485

#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int c;while(c=*rp++-48,c>=0)v=v*10+c;}
#define RDL(v) long v=0;{int c;while(c=*rp++-48,c>=0)v=v*10+c;}

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

char q[200000], *qr=q, *qw=q;
int dist[64][128][128];

static inline int isK(int a, int b , int c){
	return !a||a!=c&&(a<b&&b>c||a>b&&b<c);
}

main(){
	char*rp=mmap(0l,24l*1024,1,2,0,0ll);
	RD(w);
	RD(h);

	dist[0][0][0] = 1;
	*qw++ = 0;
	*qw++ = 0;
	*qw++ = 0;

	int z=-1;
	while(qw-qr){
		int k=*qr++;
		int y=*qr++;
		int x=*qr++;

		if(x+y==w+h-2){
			z=dist[k][y][x]-1;
			break;
		}
		int nk=rp[y*w+x<<1];
		int d;
		rep(d,4){
			int ny=y+(d==2)-(d==0);
			int nx=x+(d==3)-(d==1);
			if(ny < 0 || ny >= h || nx<0 || nx>= w) continue;
			if(!isK(k,nk,rp[ny*w+nx<<1])) continue;
			if(dist[nk][ny][nx] > 0) continue;
			dist[nk][ny][nx] = dist[k][y][x] + 1;
			*qw++ = nk;
			*qw++ = ny;
			*qw++ = nx;
		}
	}

	printf("%d",z);
}