#include<bits/stdc++.h>
#define ull unsigned long long
#define ll long long
#define all(x) x.begin(), x.end()
using namespace std;
const int maxn = 1e6 + 5;
unordered_map<int, int> D;
int sumDigit(int n){
    int sum = 0;
    while(n!=0){
        sum += n%10;
        n/=10;
    }
    return sum;
}
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int n, x;
    cin>>n;
    for(int i=1;i<=n;++i){
        cin>>x;
        D[sumDigit(x)]++;
    }
    int res = 0;
    for(auto it:D){
        if(it.second > 1){
            res += it.second * (it.second - 1) / 2;
        }
    }
    cout<<res;
}
 
 

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