题解 | #统计每个月兔子的总数#

const rl = require("readline").createInterface({ input: process.stdin });

rl.on("line", (line) => {
    var adultRabit = 0;
    var babyRabit = 1;
    var twoMonthRabit = 0;
    for (i = 1; i <= line; i++) {
        if (i <= 3) {
            var t = babyRabit;
            babyRabit = adultRabit;
            adultRabit = adultRabit + twoMonthRabit;
            twoMonthRabit = t;
        }else{
            var t = babyRabit;
            babyRabit = adultRabit + twoMonthRabit;
            adultRabit = adultRabit + twoMonthRabit;
            twoMonthRabit = t;
        }
    }
    console.log(adultRabit + babyRabit + twoMonthRabit);
});