/**
 * Greatest Common Divisor (GCD)
 * @param  {number} x First number
 * @param  {number} y Second number
 * @param  {number[]} z Additional numbers (optional)
 * @returns number The GCD of all input numbers
 * @example gcd(12, 18); // 6
 */
export declare const gcd: (x: number, y: number, ...z: number[]) => number;