int MOD;inline int mul(int a, int b){    return (long long)a * b % MOD;}int power(int a, int b){    int ret = 1;    for (int t = a; b; b >>= 1){        if (b & 1)ret = mul(ret, t);        t = mul(t, t);    }    return ret;}int cal_root(int mod){    int factor[20], num = 0, s = mod - 1;    MOD = mod--;    for (int i = 2; i * i <= s; i++){        if (s % i == 0){            factor[num++] = i;            while (s % i == 0)s /= i;        }    }    if (s != 1)factor[num++] = s;    for (int i = 2;; i++){        int j = 0;        for (; j < num && power(i, mod / factor[j]) != 1; j++);        if (j == num)return i;    }}