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

char*mmap();
static char wbuf[1<<25];

#define wbuf_end (wbuf+sizeof wbuf)
#define rd(v) long v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define rep(v,e) for(long v=0;v<e;++v)
#define reps(v,s,e) for(long v=s;v<e;++v)
#define rrep(v,e) for(long v=e;v--;)

static int base10x4[10000];

static void mkbase10(){
	long i=0;
	reps(a,'0','9'+1){
		reps(b,'0','9'+1){
			reps(c,'0','9'+1){
				reps(d,'0','9'+1){
					base10x4[i++]=a|b<<8|c<<16|d<<24;
				}
			}
		}
	}
}

typedef struct{
	int r,b,l;
}S;

static void radix_sort_aux(S*a,S*b,int n){
	int c[65536];
	for(int i=0;i<65536;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[(unsigned short)a[i].r];
	}
	int t=0;
	for(int i=65536;i--;){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		S v=a[i];
		unsigned long rb=*(unsigned long*)&v;
		long j=c[(unsigned short)rb]++;
		rb=rb<<48|rb>>16;
		*(unsigned long*)&v=rb;
		b[j]=v;
	}
}

static void radix_sort(S*a,int n){
	static S b[200000];
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
}

static S a[200000];
static int s[200000],z[200000];

main(){
	mkbase10();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);

	rd(n);
	rd(q);
	rep(i,q){
		rd(l); a[i].l=l-1;
		rd(r); a[i].r=-r;
		rd(b); a[i].b=b;
	}
	radix_sort(a,q);

	long fb=0,fi=0;
	rep(i,q){
		int b=a[i].b;
		int l=a[i].l;
		int r=-a[i].r;
		int f=(fb==b&&fi>=l);
		while(1){
			int t=l;
			while(t<r&&s[t]){
				t=s[t];
			}
			while(l!=t){
				int u=s[l];
				s[l]=t;
				l=u;
			}
			if(l>=r){
				break;
			}
			f=1;
			s[l]=l+1;
			z[l]=b;
			if(!(fb==b&&fi>=l)){
				fb=b;
				fi=l;
			}
		}
		if(!f){
			write(1,"-1\n",3);
			exit(0);
		}
	}

	char*wp=wbuf_end;
	*--wp='\n';
	rrep(i,n){
		int x=z[i];
		if(x){
			do{
				*(int*)(wp-=4)=base10x4[x%10000];
			}while(x/=10000);
			while(*wp=='0')++wp;
		}else{
			*--wp='1';
		}
		*--wp=' ';
	}
	++wp;
	write(1,wp,wbuf_end-wp);
	_exit(0);
}