//Don't have to see. start------------------------------------------
var read = require('readline').createInterface({
	input: process.stdin, output: process.stdout
});
var obj; var inLine = []; var outputList = [];var retcode = new Set();
read.on('line', function(input){
	var tmp = input.split(' ');
	for(var i = 0; i < tmp.length; i++){
		inLine.push(tmp[i]);
		if(i == tmp.length - 1){
			retcode.add(inLine.length);
		}
	}
});
read.on('close', function(){
	obj = init(inLine);
	console.error('\n↑入力 ↓出力');
	Main();
	console.log(myconv(outputList, 9));
});
function makeClone(obj){return (obj instanceof Set) ? new Set(Array.from(obj)) : JSON.parse(JSON.stringify(obj));}
function nextArray(size, code){
	var ret = new Array(size);
	for(var i = 0; i < size; i++){
		if(code == 'int'){
			ret[i] = nextInt();
		}else{
			ret[i] = next();
		}
	}
	return ret;
}
function nextIntArray(size){return nextArray(size, 'int');} function nextStrArray(size){return nextArray(size, 'str');}
function nextCharArray(){return myconv(next(),6);}
function next(){return obj.next();} function hasNext(){return obj.hasNext();} function nextInt(){return myconv(next(),1);}
function getCountMap(list){
	var map = {};
	for(var i = 0; i < list.length; i++){
		if(map[list[i]] == null){
			map[list[i]] = 0;
		}
		map[list[i]]++;
	}
	return map;
}
function init(input){  
	return {
		list : input, index : 0, max : input.length,
		hasNext : function(){return (this.index < this.max);},
		next : function(){if(this.hasNext()){return this.list[this.index++];}else{throw 'ArrayIndexOutOfBoundsException ‚There is no more input';}},
		isReturn : function(){return retcode.has(this.index);}
	};
}
function myout(s){outputList.push(s);}
function myerr(s){console.error('debug:' + require('util').inspect(s,false,null));}
function isReturn(){return obj.isReturn();}
//param "no" is
//unknown or outlier : return i. 1: parseInt.
//2: split space. 4: split space and parseInt.
//6: split 1 character. 7: split 1 character and parseInt.
//8: join space. 9: join nextline. 0: join no character.
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(' ');case 4:return i.split(' ').map(Number);case 6:return i.split('');case 7:return i.split('').map(Number);case 8:return i.join(' ');case 9:return i.join('\n');case 0:return i.join('');default:return i;}}catch(e){return i;}}

//Don't have to see. end------------------------------------------

function Main(){
	var N = nextInt();
	var M = nextInt();
	var list = new Array(M);
	var uf = new UnionFind(N);
	for(var i = 0; i < M; i++){
		var e = nextIntArray(3);
		list[i] = {
			L : e[0] - 1,
			R : e[1] - 1,
			C : e[2]
		};
	}
	list.sort(function(a,b){
		return a.C - b.C;
	});
	var output = 0;
	for(var i = 0; i < M; i++){
		var e = list[i];
		if(!uf.isSame(e.L, e.R)){
			uf.doUnion(e.L, e.R);
			output += e.C;
		}
	}
	myout(output * 2);
}
function UnionFind(n){
        var uf = {
                //全てのインデックスは「-X(親、絶対値はグループの大きさ)」「自分が属する親(≒根)」のいずれかを持つ。
                //最初はみんなグループの大きさ1の親
                'list' : new Array(n).fill(-1),
                'reset' : new Array(n),
                //同じ親を持つか
                'isSame' : function(L, R){
                        return this.getRootIndex(L) == this.getRootIndex(R);
                },
                //自身の親インデックスをたどって根っこに着く
                //親にたどり終えたら子に帰っていくついでに、子たちに「一番上の親は誰か」を知らせる
                'getRootIndex' : function(index){
                        var count = 0;
                        while(this.list[index] >= 0){
                                this.reset[count] = index;
                                index = this.list[index];
                                count++;
                        }
                        for(var i = 0; i < count; i++){
                                this.list[this.reset[i]] = index;
                        }
                        return index;
                },
                //異なる親同士のまとまりを一つにする（同じ親ならスルー）
                //小さいグループの親が大きいグループの親の直下に着く
                //グループの大きさも更新する
                'doUnion' : function(L, R){
                        var Lroot = this.getRootIndex(L);
                        var Rroot = this.getRootIndex(R);
                        if(Lroot != Rroot){
                                if(this.getSize(Lroot) >= this.getSize(Rroot)){
                                        var tmp = Lroot;
                                        Lroot = Rroot;
                                        Rroot = tmp;
                                }
                                this.list[Lroot] += this.list[Rroot];
                                this.list[Rroot] = Lroot;
                        }
                },
                //「-X(親、絶対値はグループの大きさ)」
                //なので、インデックスを指定→親を知る→親の持つグループの大きさがわかる。
                //ただしマイナス値なので、掛け算して返す。
                'getSize' : function(index){
                        return -this.list[this.getRootIndex(index)];
                }
        }
        return uf;
}