题目链接：快速幂求逆元

#include <iostream>
#include <algorithm>

using namespace std;

typedef long long LL;

LL qmi(int a, int k, int p)
{
    LL res = 1;
    while(k)
    {
        if(k & 1) res = (LL) res * a % p;
        k >>= 1;
        a = (LL) a * a % p;
    }
    
    return res;
}

int main()
{
    int n;
    scanf("%d", &n);
    while(n --)
    {
        int a, p;
        scanf("%d%d", &a, &p);
        int t = qmi(a, p - 2, p);
        if(a % p) printf("%d\n", t);
        else printf("impossible\n");
    }
    
    return 0;
}