text: 'use strict';
  
  const fs = require('fs');
  
  process.stdin.resume();
  process.stdin.setEncoding('utf-8');
  
  let inputString = '';
  let currentLine = 0;
  
  process.stdin.on('data', inputStdin => {
      inputString += inputStdin;
  });
  
  process.stdin.on('end', _ => {
      inputString = inputString.replace(/\s*$/, '')
          .split('\n')
          .map(str => str.replace(/\s*$/, ''));
  
      main();
  });
  
  function readLine() {
      return inputString[currentLine++];
  }
  
  // Complete the arrayManipulation function below.
  function arrayManipulation(n, queries) {
  
  let arr = [];
  let max = 0;
  for (let l = 0; l < n; l++) {
  arr[l] = 0;
  }
  for (let i = 0; i < queries.length; i++) {
  arr[queries[i][0]-1] += queries[i][2];
  if (queries[i][1] < arr.length) {
  arr[queries[i][1]] -= queries[i][2];
  }
  }
  for (let j = 1; j < n; j++) {
  arr[j] += arr[j-1];
  }
  for (let k = 0; k < arr.length; k++) {
  max = Math.max(max, arr[k]);
  }
  return max;
  }
  
  
  function main() {
      const ws = fs.createWriteStream(process.env.OUTPUT_PATH);
  
      const nm = readLine().split(' ');
  
      const n = parseInt(nm[0], 10);
  
      const m = parseInt(nm[1], 10);
  
      let queries = Array(m);
  
      for (let i = 0; i < m; i++) {
          queries[i] = readLine().split(' ').map(queriesTemp => parseInt(queriesTemp, 10));
      }
  
      let result = arrayManipulation(n, queries);
  
      ws.write(result + "\n");
  
      ws.end();
  }
  