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- #include <iostream>
- #include <vector>
- using namespace std;
- int main(){
- vector<int> num(12, 0);
- int n;
- cin>>n;
- int a;
- for(int i=0;i<n;i++){
- cin>>a;
- num[a%12]++;
- }
- int ans=0;
- int ans2=0;
- int ans3=0;
- for(int i=0;i<12;i++){
- for(int j=0;j<12;j++){
- for(int k=0;k<12;k++){
- if( (i+j+k) % 12 == 0){
- if(i==j && j==k){
- ans+=num[i]*(num[j]-1)*(num[j]-2)/6;
- }
- else if(i==j){
- ans2+=num[k]*num[i]*(num[j]-1)/2;
- }
- else if(i==k){
- ans2+=num[j]*num[i]*(num[k]-1)/2;
- }
- else if(j==k){
- ans2+=num[i]*num[j]*(num[k]-1)/2;
- }
- else{
- ans3+=num[i]*num[j]*num[k];
- }
- }
- }
- }
- }
- cout<<ans+ans2/3+ans3/6;
- }
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