#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;}

rs[1000],rn;

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	RD(n);
	char*s=rp;
	char*t=rp+(n*2+1);
	int rn=0;
	for(int i=0;i<n;++i){
		int s0=s[i];
		int s1=s[i+n];
		int s2=s0^s1^'0';
		int t0=t[i];
		int t1=t[i+n];
		if(t0==s0&&t1==s1){
		}else if(t0==s2&&t1==s0){
			rs[rn++]=i;
			rs[rn++]=i+1;
		}else if(t0==s1&&t1==s2){
			rs[rn++]=i+n;
			rs[rn++]=i+n+1;
		}else{
			puts("-1");
			exit(0);
		}
	}
	if(rn>0&&rs[rn-1]==n*2){
		rs[rn-1]=0;
	}
	printf("%d\n",rn);
	for(int i=0;i<rn;++i){
		printf("%d\n",rs[i]);
	}
}