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export default function findTheDifference(s: string, t: string): string {    const cnt = new Map<string, number>();
    Array.prototype.forEach.call(t, (v) => cnt.set(v, 1 + (cnt.get(v) || 0)));
    Array.prototype.forEach.call(s, (v) => cnt.set(v, -1 + (cnt.get(v) || 0)));
    return [...cnt.entries()].filter((a) => a[1])[0][0];}