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function countAndSay(n: number): string {    const cached = cache.get(n);
    if (cached) {        return cached;    }
    const sb: string[] = [];
    if (n === 1) {        sb.push("1");    } else {        let prev = countAndSay(n - 1);        if (prev.length === 1) {            sb.push("" + "1" + prev);        } else {            while (prev.length) {                const start = prev[0];                if (prev[1] && start !== prev[1]) {                    sb.push("" + "1" + start);                    prev = prev.slice(1);                } else {                    const index = Array.prototype.findIndex.call(                        prev,                        (v) => v !== start,                    );
                    if (index >= 0) {                        sb.push("" + index + start);                        prev = prev.slice(index);                    } else {                        sb.push("" + prev.length + start);                        prev = "";                    }                }            }        }    }    const res = sb.join("");
    cache.set(n, res);    return res;}
const cache = new Map<number, string>();export default countAndSay;