数列那个题刚开始我也是暴力，提示运行超时，然后突然发现一个规律：
123，456， 789， 101112....每相邻三个一组的数据中必定有两个能够被三整除

var readline = require('readline');
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal:false
});
function computed(n){
    var g = Math.floor(n / 3);
    var l = n % 3 ;
    if(l == 0 || l== 1){
        return g * 2;
    }else if(l == 2){
        return g * 2 + 1;
    }
}

rl.on('line', function(line){ 
    var tokens = line.split(' ');
    var start = Number(tokens[0]),
        end = Number(tokens[1]);

    console.log(computed(end) - computed(start - 1));
});