[NOI2010]：能量采集

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#define ll long long
using namespace std;
const int N=1e5+5;
int n,m;
ll f
,ans;
int main(){
scanf("%d %d",&n,&m);
if(n>m)swap(n,m);
for(int i=n;i>=1;i--){
f[i]=(ll)(n/i)*(ll)(m/i);
for(int j=(i<<1);j<=n;j+=i)f[i]-=f[j];
ans+=(ll)((i<<1)-1)*f[i];
}
printf("%lld",ans);
return 0;
}