I would like you to read the full story and give me some feedback on it, Thank You.

Today I was solving this amazing 715A - Plus and Square Root problem. After finding the idea and implementing it in C++, I submitted it in C++17 and later in C++20.

But I was getting the wrong answers in the main test 5. At first, I thought my idea was wrong and I tried to prove my idea. Thinking about the problem the whole day I got nothing wrong with my approach and implementation.

By not finding any other way I opened my submission and then I saw the reasons for the wrong answer 198441320. But in theory and my implementation method, there could not have errors such as this.

After that, I got experimental and tested the code, and changed certain bits. But whatever I did it didn't change the verdict.

The main part of my code was:

ll lcm(ll a, ll b){
    ll LCM = (a * b);
    return LCM;
}
void solve(){
    
    ll n;
    scl(n); // scan in long long

    ll LCM = 2;

    for(int i = 1; i <= n; i++){
        ll templcm = lcm(i, i + 1);
        ll res = (templcm - LCM) / i + (templcm / i) * (templcm - 1);      
        cout << res << endl;
        LCM = templcm;
    }
    return;
}

But after that, I submitted the same code with the change of variable type of i (loop Variable) that got AC 198513530.

// Previous codes are unchanged

for(ll i = 1; i <= n; i++){
    ll templcm = lcm(i, i + 1);
    ll res = (templcm - LCM) / i + (templcm / i) * (templcm - 1);      
    cout << res << endl;
    LCM = templcm;
}    

Here I should not have got this verdict because in whatever the type of i (loop Variable) be, it should be converted to long long.

Now I was having fun, in another version: I have declared another variable j, and did this and that also got an AC:

 for(int i = 1; i <= n; i++){
        ll templcm = lcm(i, (i + 1) ), templcm2 = lcm(j, j + 1);
        templcm = templcm2;
        ll res = (templcm - LCM) / i + (templcm / i) * (templcm - 1);
        if(templcm != templcm2){
            cout << templcm << " " << templcm2 << endl;
        }
        cout << res << endl;
        LCM = templcm;
        j++;
    }

Finally, I submitted my first submission (Where i in int type) 198505674 in C++14 and with the help of magic it got AC That same code that got WA in C++ 17 and C++20 got AC in C++14.