#include<cstdio>
#include<iostream>
#include<string>
#include<cstring>
#include<queue>
#include<vector>
#include<stack>
#include<vector>
#include<map>
#include<set>
#include<algorithm>
#include<cmath>
//#include<bits/stdc++.h>
using namespace std;typedef long long ll;const int maxn = 1e5;
bool isNot[maxn];void seive(int n = maxn-1)
{int m = sqrt(n+0.5);for(int i = 2; i <= m; i++){if(!isNot[i])for(int j = i*i; j <= n; j += i){isNot[j] = true;}}isNot[0] = isNot[1] = true;
}int d[maxn];
int vis[2][maxn],clk;
#define PB push_back
#define PS push
const int wei[] = {1,10,100,1000};void doubleBfs(int s,int t)
{if(s == t) { puts("0"); return; }queue<int> Q[3];queue<int> *q1 = Q, *q2 = Q+1, *nxt = Q+2;int *v1 = *vis, *v2 = vis[1];q1->PS(s); q2->PS(t);v1[s] = ++clk; v2[t] = clk;d[s] = 0; d[t] = 0;while(q1->size() && q2->size()){if(q1->size()>q2->size()){swap(q1,q2); swap(v1,v2);}while(q1->size()){int u = q1->front(); q1->pop();int dig[4];for(int i = 0; i < 4; i++){dig[i] = u/wei[i]%10;}for(int i = 0; i < 4; i++){int t = u - dig[i]*wei[i];for(int j = i == 3; j < 10; j++){if(j != dig[i]){int v = t+j*wei[i];if(!isNot[v] && v1[v] != clk){if(v2[v] == clk) {printf("%d\n",d[v]+d[u]+1);return;}d[v] = d[u]+1;nxt->PS(v);v1[v] = clk;}}}}}swap(q1,nxt);}puts("Impossible");
}//#define LOCAL
int main()
{
#ifdef LOCALfreopen("in.txt","r",stdin);
#endifseive();int T; scanf("%d",&T);while(T--){int a,b; scanf("%d%d",&a,&b);doubleBfs(a,b);}return 0;
}