莫比乌斯反演
双倍经验美滋滋
不多解释了。。。划水划水
#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 50005
#define F inline
using namespace std;
int n,a,b,k,t,nd,p[N],mu[N],sum[N];
bool f[N];
F char readc(){
static char buf[100000],*l=buf,*r=buf;
if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);
if (l==r) return EOF; return *l++;
}
F int _read(){
int x=0; char ch=readc();
while (!isdigit(ch)) ch=readc();
while (isdigit(ch)) x=(x<<3)+(x<<1)+(ch^48),ch=readc();
return x;
}
F void mkp(){
for (int i=2;i<N;i++){
if (!f[i]) p[++nd]=i,mu[i]=-1;
for (int j=1,v;j<=nd&&(v=i*p[j])<N;j++){
f[v]=true,mu[v]=-mu[i];
if (i%p[j]==0) { mu[v]=0; break; }
}
}
for (int i=1;i<N;i++) sum[i]=sum[i-1]+mu[i];
}
F int calc(int n,int m){
if (n>m) swap(n,m); int ans=0,p;
for (int i=1;i<=n;i=p+1){
p=min(n/(n/i),m/(m/i));
ans+=(sum[p]-sum[i-1])*(n/i)*(m/i);
}
return ans;
}
int main(){
t=_read(),mu[1]=1,mkp();
while (t--){
a=_read(),b=_read(),k=_read(),a/=k,b/=k;
printf("%d\n",calc(a,b));
}
return 0;
}