YbtOJ 最小数

#include<bits/stdc++.h>
#define Tp template<typename Ty>
#define Ts template<typename Ty,typename... Ar>
#define W while
#define I inline
#define RI register int
#define LL __int128
#define int LL
#define Cn const
#define CI Cn int&
#define gc getchar
#define D isdigit(c=gc())
#define pc(c) putchar((c))
#define min(x,y) ((x)<(y)?(x):(y))
#define max(x,y) ((x)>(y)?(x):(y))
using namespace std;
namespace Debug{
    Tp I void _debug(Cn char* f,Ty t){cerr<<f<<'='<<t<<endl;}
    Ts I void _debug(Cn char* f,Ty x,Ar... y){W(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
    Tp ostream& operator<<(ostream& os,Cn vector<Ty>& V){os<<"[";for(Cn auto& vv:V) os<<vv<<",";os<<"]";return os;}
    #define gdb(...) _debug(#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
namespace FastIO{
    Tp I void read(Ty& x){char c;int f=1;x=0;W(!D) f=c^'-'?1:-1;W(x=(x<<3)+(x<<1)+(c&15),D);x*=f;}
    Ts I void read(Ty& x,Ar&... y){read(x),read(y...);}
    Tp I void write(Ty x){x<0&&(pc('-'),x=-x,0),x<10?(pc(x+'0'),0):(write(x/10),pc(x%10+'0'),0);}
    Tp I void writeln(Cn Ty& x){write(x),pc('\n');}
}using namespace FastIO;
int Tt,n,Ans;
vector<int> v; 
I int phi(RI m){
    RI i,S,t;for(S=m,i=2;i*i<=m;i++) if(!(m%i)){
        S=1LL*S/i*(i-1);W(!(m%i)) m/=i;
    }if(m>1) S=1LL*S/m*(m-1);return S;
}
I int QP(RI a,RI b,CI p){RI s=1;W(b) b&1&&(s=1LL*s*a%p),a=1LL*a*a%p,b>>=1;return s;}
signed main(){
    RI i,t;W(read(n),n){
        printf("Case "),++Tt,write(Tt),pc(':'),pc(' '),Ans=0;
        if(n%16&&n%5){
            if(!(n&1)) n>>=1;
            if(!(n&1)) n>>=1;
            if(!(n&1)) n>>=1;
            n*=9,t=n;n=phi(n);
            for(i=1;i*i<=n;i++) if(!(n%i)) v.push_back(i),v.push_back(n/i);
            sort(v.begin(),v.end());for(auto i:v) if(QP(10,i,t)==1){Ans=i;break ;}
        }writeln(Ans);
    }return 0;
}