1700A - Optimal Path - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
#define int long long 
#define vi vector<int>
#define vvi vector<vector<int> > 
#define pii pair<int,int> 
#define ff first
#define ss second
#define m_p make_pair
#define sz(x) ((int)(x).size())
#define ld long double
const int mod = 1e9 + 7;

#ifndef ONLINE_JUDGE
#define debug(x) cerr << #x<<" "; _print(x); cerr << endl;
#else
#define debug(x);
#endif

void _print(int t) {cerr << t;}
void _print(string t) {cerr << t;}
void _print(char t) {cerr << t;}
void _print(ld t) {cerr << t;}
void _print(double t) {cerr << t;}

template <class T, class V> void _print(pair <T, V> p);
template <class T> void _print(vector <T> v);
template <class T> void _print(set <T> v);
template <class T, class V> void _print(map <T, V> v);
template <class T> void _print(multiset <T> v);
template <class T, class V> void _print(pair <T, V> p) {cerr << "{"; _print(p.ff); cerr << ","; _print(p.ss); cerr << "}";}
template <class T> void _print(vector <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T> void _print(set <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T> void _print(multiset <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T, class V> void _print(map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}

//************************************************************************//

int expo(int a, int b, int mod) {int res = 1; while (b > 0) {if (b & 1)res = (res * a) % mod; a = (a * a) % mod; b = b >> 1;} return res;}
int inv(int i) {if (i == 1) return 1; return (mod - ((mod / i) * inv(mod % i)) % mod) % mod;}
int mod_mul(int a, int b) {a = a % mod; b = b % mod; return (((a * b) % mod) + mod) % mod;}
int mod_add(int a, int b) {a = a % mod; b = b % mod; return (((a + b) % mod) + mod) % mod;}
int gcd(int a, int b) { if (b == 0) return a; return gcd(b, a % b);}
int ceil_div(int a, int b) {return a % b == 0 ? a / b : a / b + 1;}

//****************************Template Ends*******************************//

void solve(){
    int n,m;
    cin>>n>>m;
    int ans=0;
    int a = n*m*(n-1)/2;
    int b = m*(m+1)/2;
    int c = (n-1)*m;
    
    ans = a+b+c;
    cout<<ans<<'\n';
    
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    #ifndef ONLINE_JUDGE
      freopen("input.txt", "r", stdin);
      freopen("output.txt", "w", stdout);
      freopen("error.txt" , "w" , stderr);
    #endif
   
    
    auto start1 = high_resolution_clock::now();
    int T;
    cin >> T;
    while (T--) {
       solve();
    }
    auto stop1 = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(stop1 - start1);
    
    #ifndef ONLINE_JUDGE
        cout << "Time: " << duration . count() / 1000 << endl;
    #endif
    
    return 0;
}