type Elem = "I" type Formattable = string | number | bigint | boolean | null | undefined type NumToArr = Acc["length"] extends N ? Acc : NumToArr type TupleToString = T extends [infer T1 extends Formattable, ...infer T2] ? TupleToString : Acc type Repeat = Acc["length"] extends N ? Acc : Repeat type RepeatString = TupleToString> type Reverse = S extends `${infer S1}${infer S2}` ? `${Reverse}${S1}` : "" type StringLength = S extends `${infer S1}${infer S2}` ? StringLength : Count["length"] type PadZero = NumToArr extends [...NumToArr>, ...infer Rest] ? `${RepeatString<"0",Rest["length"]>}${S}` : S type Padded = [ `0${PadZero>,StringLength>}`, `0${PadZero>,StringLength>}`] type TrimLeadingZeros = S extends "0" ? S : S extends `0${infer S2}` ? TrimLeadingZeros : S type CarryOut = Arr extends [...Repeat, ...infer Rest] ? [1, Rest["length"]] : [0, Arr["length"]] type SumOneDigit = CarryIn extends 1 ? CarryOut<[...NumToArr, ...NumToArr, Elem]> : CarryOut<[...NumToArr, ...NumToArr]> type SumReverse = NS extends `${infer X extends number}${infer NRest}` ? MS extends `${infer Y extends number}${infer MRest}` ? SumOneDigit extends [infer CarryOut extends 0|1, infer Result extends number] ? SumReverse : never : never : `${Acc}` type Sum = Padded<`${A}`,`${B}`> extends [infer A2 extends string, infer B2 extends string] ? TrimLeadingZeros, Reverse>>> : never type MulOneDigit< N extends number, M extends number, Count extends readonly unknown[]=[], Acc extends readonly unknown[]=[]> = Count["length"] extends M ? Acc["length"] : MulOneDigit]> type Mul10 = `${S}0` type MulByOneDigit = NS extends `${infer X extends number}${infer NRest}` ? MulOneDigit extends infer Result extends number ? MulByOneDigit, Result>> : never : Acc type MulImpl = MS extends `${infer Y extends number}${infer MRest}` ? MulImpl, MulByOneDigit>> : Acc type Multiply ~~= TrimLeadingZeros>~~