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function repeatedCharacter(s: string): string {    let bitset = 0n;    for (const char of s) {        const num = BigInt(            1n << BigInt(char.charCodeAt(0) - "a".charCodeAt(0) + 1),        );        if (bitset & num) {            return char;        }        bitset |= num;        // console.log(bitset,num)    }    return s[0];}export default repeatedCharacter;