tt

int lastDigitDiffZero(long n) {
    long a = fact(n);
    if(a < 10000) {
        long last= a % 10;
        while (a % 10 == 0) {
            a /= 10;
            last =a%10;
        }
        return (int)last;
    }
    BigInteger f = factorial(n);
    BigInteger b2 = new BigInteger("10");
    BigInteger b3 = BigInteger.ZERO;

   while (f.mod(new BigInteger("10")).equals(BigInteger.ZERO)) {
        f = f.divide(b2);
        b3 = f.mod(new BigInteger("10"));
    }
    return b3.intValue();
}

BigInteger factorial(long n) {
    BigInteger result = BigInteger.ONE;
    for (; n > 1; n--) {
        result = result.multiply(BigInteger.valueOf(n));
    }
    return result;
}

int fact(long n) {
    int f = 0;
    for (int c = 1; c <= n; c++) {
            f *= c;
    }
    return f;
}