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const capacity = Symbol();const stacks = Symbol();class StackOfPlates {    [stacks]: number[][] = [];    [capacity]: number;    constructor(cap: number) {        this[capacity] = cap;    }
    push(val: number): void {        if (this[capacity] <= 0) return;
        if (            this[stacks].length === 0 ||            this[stacks][this[stacks].length - 1].length >= this[capacity]        ) {            this[stacks].push([val]);        } else {            this[stacks][this[stacks].length - 1].push(val);        }    }
    pop(): number {        if (this[capacity] <= 0) return -1;        if (this[stacks].length === 0) return -1;
        const lastStack = this[stacks][this[stacks].length - 1];        const val = lastStack.pop();        if (lastStack.length === 0) {            this[stacks].pop();        }        return val ?? -1;    }
    popAt(index: number): number {        if (this[capacity] <= 0) return -1;        if (this[stacks].length === 0) return -1;        const currentStack = this[stacks][index];        if (!currentStack) {            return -1;        }        const val = currentStack.pop();        if (currentStack.length === 0) {            this[stacks].splice(index, 1);        }        return val ?? -1;    }}export default StackOfPlates;