Codeforces Round #273 (Div. 2) 478B - Random Teams Solution

Problem Link :   https://codeforces.com/problemset/problem/478/B 

Solution in C++:

///La ilaha illellahu muhammadur rasulullah

///******Bismillahir-Rahmanir-Rahim******///

///Abul Hasnat  Tonmoy

///Department of CSE,23rd batch

///Islamic University,Bangladesh

#include <bits/stdc++.h>

using namespace std;

int main()

{

    long long n,m,r,s,e,a,k,i;

    while(cin>>n>>m)

    {

        s=0;

        ///mn

        if(n%m==0)

        {

            a=(n/m)-1;

            for(i=1; i<=m; i++)

                s+=(a*(a+1))/2;

        }

        else

        {

            e=n%m;

            a=n/m;

            for(i=1; i<=e; i++)

                s+=(a*(a+1))/2;

            r=m-e;

            k=(n/m)-1;

            for(i=1; i<=r; i++)

                s+=(k*(k+1))/2;

        }

        cout<<s<<" ";

        ///mx

        k=n-(m-1);

        r=k-1;

        cout<<(r*(r+1))/2<<endl;

    }

}