CF 272 B. Dima and Sequence

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
typedef long long ll;
const int maxn=100002;
ll sum,ans,cnt[112];
int main()
{
//freopen("//media/学习/ACM/input.txt","r",stdin);
int n,a,i,j,mmax;
while(scanf("%d",&n)!=EOF)
{
memset(cnt,0,sizeof(cnt));
for(mmax=ans=i=0;i<n;i++)
{
cin>>a;
sum=0;
while(a)
{
sum+=a%2;
a/=2;
}
cnt[sum]++;
if(mmax<sum)mmax=sum;
}
for(i=0;i<=mmax;i++)
if(cnt[i]>=2)ans+=cnt[i]*(cnt[i]-1)/2;
cout<<ans<<endl;
}
return 0;
}