int A[1d7],H,W,i,z,t;
int f(int i){
	return A[i]=A[i]-i?f(A[i]):i;
}
{
	rd(H,W);
	rep(i,W+1,~H*~W){i%~W||++i;rd(t);if(A[i]=t*i)rep(j,2)if(t=f(i-1-j*W))A[f(i)]=t;}
	for(;--i;)z+=i==f(i);
	wt(z);
}