var input = require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");
var obj = {
  "list" : input,
  "index" : 0,
  "max" : input.length,
  "next" : function(){
    if(!this.hasNext()){throw "NoSuchElementException:次に要素は無いよ";}
    var returnObj = this.list[this.index];
    this.index++;
    return returnObj;
  },
  "hasNext" : function(){return (this.index < this.max);}
}

function next(){return obj.next();}
function hasNext(){return obj.hasNext();}
function myout(t){console.log(t);}//standard output
function myerr(t){console.error(t);}//standard error
//[no]要素の扱い。数値型
//不明値、異常時:引数そのまま返す　1:数値へ変換
//2:半角SPで分割 4:半角SPで分割し、数値配列へ
//6:1文字で分割  7:1文字で分割し、数値配列へ
//8:半角SPで結合 9:改行で結合 0:文字なしで結合
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(" ");case 4:return i.split(" ").map((a)=>Number(a));case 6:return i.split("");case 7:return i.split("").map((a)=>Number(a));case 8:return i.join(" ");case 9:return i.join("\n");case 0:return i.join("");default:return i;}}catch(e){return i;}}
function Main(){
  var one = myconv(next(),4);
  var N = one[0];
  var M = one[1];
  if(M == 0){
     if(N == 1){
        myout(0);
     }else{
        myout(-1);
     }
    return;
  }
  var list = new Array(N);
  while(hasNext()){
    var tmp = myconv(next(),4);
    if(tmp[0] == 1 && tmp[1] == 0){
       continue;
    }
    if(!list[tmp[0] - 1]){
       list[tmp[0] - 1] = tmp[1];
    }else{
      list[tmp[0] - 1] = Math.min(list[tmp[0] - 1],tmp[1]);
    }
  }
  if(N != 1 && (list[0] == 0 || list[0] == null)){
     myout(-1);
    return;
  }else{
    if(N == 1 && list[0] == null){
       list[0] = 0;
    }
    if(N >= 2 && list[1] == null){
       list[1] = 0;
    }
    if(N == 3 && list[2] == null){
       list[2] = 0;
    }
  }
  myout(myconv(list,0));
}
Main();