const readline = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
});

const input = [];
readline.on('line', (line) => {
    input.push(line.split(' ').map(v=> Number(v)));
});

readline.on('close',()=> {
    input.shift()
    console.log(merge(input));
})

/**
 * 区间合并
 * @param {Array} intervals 区间数组 [[1, 3], [2, 6], [8, 10], [15, 18]]
 * @return {number} 合并后的区间数量
 **/
function merge(intervals) {
  if (intervals.length === 0) return 0;
  if (intervals.length === 1) return 1;
  // 对所有的区间按照左端点进行升序排序
  intervals.sort((a, b) => a[0] - b[0])
  // 定义一个新的数组，用于存储合并后的区间
  const merged = [intervals[0]];
  // 遍历所有的区间
  for (let i = 0; i < intervals.length; i++) {
    // 如果当前区间左端点小于等于上一个区间的右端点，则说明两个区间有重叠
    const [currentLeft, currentRight] = intervals[i];
    const lasrMerge = merged[merged.length - 1];
    if (currentLeft <= lasrMerge[1] && currentRight >= lasrMerge[1]) {
      // 合并两个区间并且存入新的数组中
      lasrMerge[1] = currentRight;
    } else if (currentLeft > lasrMerge[1]) {
      merged.push(intervals[i]);
    }
  }
  return merged.length;
}