Submission #66560988

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Source Code Expand

#include <bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
int n, m;
void solve()
{
    // Add your solution here
    int n,l;
    cin>>n>>l;
    vector<int>v(l);
    map<int,int>mp;
    mp[0]++;
    int pos=0;
    for(int i=0 ; i<n-1 ; i++){
        int d;
        cin>>d;
        int npos = pos+d;
        npos = (npos%l+l)%l;
        mp[npos]++;
        pos=npos;
    }
    int ans=0;
    if(l%3==0){
        int ele = (l/3);

        for(int i=0 ; i<l ; i++){
            int res=1;
            int x = i;
            int y = ((i+ele)%l+l)%l;
            int z = ((i+2*ele)%l+l)%l;

            if(x==y || y==z || z==x) continue;
            // int res =1;
            res*=mp[x];
            res*=mp[y];
            res*=mp[z];
            ans+=res;
        }
        ans=ans/3;
        cout<<ans<<endl;
    }
    else{
        cout<<0<<endl;
    }

}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int t;
    t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}

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