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不會，先坑著

https://kelin.blog.luogu.org/solution-p1587

 1 //minamoto
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<algorithm>
 5 using namespace std;
 6 const int N=7e5+5,E=2e6+5;
 7 typedef int arr[N];typedef long long ll;
 8 struct Am{int nx,x,w;}e1[E];
 9 struct Ans{int
 
 nx,n,m,k;ll w;}e2[E];
10 int n,m,k,M,c1,c2,K[2005],f1[E],f2[E];arr vis,p,mu,sum;
11 int Sm(int x){
12     if(x<=M) return sum[x];
13     int u=(x+2017)%E;
14     for(int i=f1[u];i;i=e1[i].nx)
15     if(e1[i].x==x) return e1[i].w;
16     e1[++c1]=(Am){f1[u],x,1},f1[u]=c1;
17     int &w=e1[c1].w,i=2
 
,j=sqrt(x);
18     for(;i<=j;++i) w-=Sm(x/i);
19     for(;i<=x;i=j+1)
20     j=x/(x/i),w-=(j-i+1)*Sm(x/i);
21     return w;
22 }
23 ll sol(int n,int m,int k){
24     if(!n||!m) return 0;
25     int u=(2017ll*n+m+k)%E;
26     for(int i=f2[u];i;i=e2[i].nx)
27     if(e2[i].n==n&&e2[i].m==m&&e2[i].k==k) return
 
 e2[i].w;
28     e2[++c2]=(Ans){f2[u],n,m,k,0},f2[u]=c2;ll &w=e2[c2].w;
29     if(k==1){
30         if(n>m) swap(n,m);
31         int i=1,j=sqrt(n),s,t=0,x,y;
32         for(;i<=j;++i,t=s) s=Sm(i),w+=1ll*(n/i)*(m/i)*(s-t);
33         for(;i<=n;i=j+1,t=s)x=n/i,y=m/i,j=min(n/x,m/y),s=Sm(j),w+=1ll*x*y*(s-t);
34         u=(2017ll*m+n+k)%E;e2[++c2]=(Ans){f2[u],m,n,k,w},f2[u]=c2;
35     }
36     else for(int i=1;i<=K[0]&&K[i]<=k;++i)
37     if(k%K[i]==0&&mu[K[i]])
38     w+=sol(m/K[i],n,K[i])*mu[K[i]];
39     return w;
40 }
41 int main(){
42 //    freopen("testdata.in","r",stdin);
43     scanf("%d%d%d",&n,&m,&k);
44     M=min(N-5,max(k,min(n,m))),sum[1]=mu[1]=1;
45     for(int i=2;i<=M;++i){
46         if(!vis[i]) p[++p[0]]=i,mu[i]=-1;
47         for(int j=1,x;j<=p[0]&&(x=i*p[j])<=M;++j){
48             vis[x]=1;
49             if(i%p[j]==0) break;
50             mu[x]=-mu[i];
51         }
52         sum[i]=sum[i-1]+mu[i];
53     }
54     for(int i=1;i<=k;++i)
55     if(k%i==0) K[++K[0]]=i;
56     printf("%lld\n",sol(n,m,k));
57     return 0;
58 }

洛谷P1587 [NOI2016]循環之美