1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5 #include 
         
           6 #include 
          
            7 #define MAXN 10000 8 using namespace std; 9 10 int first,last;11 int prime[MAXN];12 void dabiao()13 {14 int i,j;15 for(i = 1000;i
           

q;35 memset(dis,0,sizeof(dis));36 memset(vis,0,sizeof(vis));37 q.push(first);38 vis[first] = 1;39 while(!q.empty())40 {41 int x = q.front();42 q.pop();43 t[0] = x/1000;44 t[1] = x%1000/100;45 t[2] = x%100/10;46 t[3] = x%10;47 if(x == last)48 return dis[x];49 for(i = 0;i<4;i++)50 {51 int temp = t[i];52 for(j = 0;j<10;j++)53 {54 if(temp != j)55 {56 t[i] = j;57 v = t[0]*1000+t[1]*100+t[2]*10+t[3];58 if(!vis[v]&&prime[v])59 {60 vis[v] = 1;61 dis[v] = dis[x]+1;62 q.push(v);63 }64 if(v == last)65 return dis[v];66 }67 t[i] = temp;68 }69 }70 }71 return -1;72 }73 74 int main()75 {76 //freopen("caicai.txt","r",stdin);77 int n;78 scanf("%d",&n);79 dabiao();80 while(n--)81 {82 cin>>first>>last;83 int num = bfs();84 if(num == -1)85 cout<<"Impossible\n";86 else cout<

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