process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function main() {
    var n_temp = readLine().split(' ');
    var listSize = parseInt(n_temp[0]);
    var lineNumber = parseInt(n_temp[1]);
    let slopList = new Array();
    for(let i = 0;i < listSize;i++){
        slopList.push(0);
    }

    for(var a0 = 0; a0 < lineNumber; a0++){
        var a_temp = readLine().split(' ');

        const beginElementPos = parseInt(a_temp[0]);
        const endElementPos = parseInt(a_temp[1]);
        const addValue = parseInt(a_temp[2]);
        slopList[beginElementPos-1] += addValue;
        if (endElementPos<listSize){
          slopList[endElementPos]-=addValue;
        }
    }
    let actualList = new Array();
    let sum = 0;
    for (let i=0; i<listSize; i++) {
        sum += slopList[i];
        actualList.push(sum);
    }

   let max =  actualList.reduce((acc,val)=>{

        return (acc>val)?acc:val;
    },0);
    console.log(max);

}