Count5

#include <iostream>
using namespace std;
int a[82];

short int suma(int n)
{
    short int s=0;
    while(n)
        s+=n%10,n/=10;
    return s;
}

int main()
{
    int n;
    cin>>n;
    int x;
    for(int i=1;i<=n;++i)
        cin>>x,++a[suma(x)];
    unsigned long long int sol=0;
    for(int i=1;i<82;++i)
        if(a[i]>1)
            sol+=a[i]*(a[i]-1)/2;
    cout<<sol;
    return 0;
}