求最小的n，使phi（n）=m

 

#include
     
      #include
      
       #define N 10011int prime[N],cnt;bool v[N],vis[N];int p[N],tot,ans;void pre_prime(){    for(int i=2;i
       
        =N) break;            v[i*prime[j]]=1;            if(i%prime[j]==0) break;        }    }}int judge(int n){    if(n==1) return 1;    n++;    for(int i=1;i<=cnt && prime[i]*prime[i]<=n;i++)        if(n%prime[i]==0) return -1;    for(int i=1;i<=tot;i++)        if(vis[i] && n==p[i]) return -1;    return n;}void dfs(int now,int left,int sum){    if(sum==tot+1)    {        int ret=judge(left);        if(ret>0) ans=std::min(ans,now*ret);        return;    }    dfs(now,left,sum+1);    if(left%(p[sum]-1)==0)    {        vis[sum]=1;        now*=p[sum];        left/=p[sum]-1;        while(1)        {            dfs(now,left,sum+1);            if(left%p[sum]) break;            left/=p[sum];now*=p[sum];        }        vis[sum]=0;    }}void solve(int n){    tot=0; ans=2e9;    for(int i=1;i<=cnt && n>=(prime[i]-1)*(prime[i]-1);i++)        if(n%(prime[i]-1)==0)         p[++tot]=prime[i];    dfs(1,n,1);}int main(){    pre_prime();    int n,t=0;    while(scanf("%d",&n)!=EOF)    {        if(!n) return 0;        solve(n);        printf("Case %d: %d %d\n",++t,n,ans);    }}