Language: C++

√#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<string> a(3);
  for (int i=0; i<3; i++) {
    cin >> a[i];
    if (a[i].at(0)=='a') {
      cout << 'A';
    }
    if (a[i].at(0)=='b') {
      cout << 'B';
    }
    if (a[i].at(0)=='c') {
      cout << 'C';
    }
    if (a[i].at(0)=='d') {
      cout << 'D';
    }
    if (a[i].at(0)=='e') {
      cout << 'E';
    }
    if (a[i].at(0)=='f') {
      cout << 'F';
    }
    if (a[i].at(0)=='g') {
      cout << 'G';
    }
    if (a[i].at(0)=='h') {
      cout << 'H';
    }
    if (a[i].at(0)=='i') {
      cout << 'I';
    }
    if (a[i].at(0)=='j') {
      cout << 'J';
    }
    if (a[i].at(0)=='k') {
      cout << 'K';
    }
    if (a[i].at(0)=='m') {
      cout << 'M';
    }
    if (a[i].at(0)=='n') {
      cout << 'N';
    }
    if (a[i].at(0)=='o') {
      cout << 'O';
    }
    if (a[i].at(0)=='p') {
      cout << 'P';
    }
    if (a[i].at(0)=='q') {
      cout << 'Q';
    }
    if (a[i].at(0)=='r') {
      cout << 'R';
    }
    if (a[i].at(0)=='s') {
      cout << 'S';
    }
    if (a[i].at(0)=='t') {
      cout << 'T';
    }
    if (a[i].at(0)=='u') {
      cout << 'U';
    }
    if (a[i].at(0)=='v') {
      cout << 'V';
    }
    if (a[i].at(0)=='w') {
      cout << 'W';
    }
    if (a[i].at(0)=='x') {
      cout << 'X';
    }
    if (a[i].at(0)=='y') {
      cout << 'Y';
    }
    if (a[i].at(0)=='z') {
      cout << 'Z';
    }
  }
  cout << endl;
}


Compiler output:
a.cc:1:1: error: extended character √ is not valid in an identifier
    1 | √#include <bits/stdc++.h>
      | ^
a.cc:1:2: error: stray '#' in program
    1 | √#include <bits/stdc++.h>
      |  ^
a.cc:1:1: error: '\U0000221a' does not name a type
    1 | √#include <bits/stdc++.h>
      | ^
a.cc: In function 'int main()':
a.cc:4:3: error: 'vector' was not declared in this scope
    4 |   vector<string> a(3);
      |   ^~~~~~
a.cc:4:10: error: 'string' was not declared in this scope
    4 |   vector<string> a(3);
      |          ^~~~~~
a.cc:4:18: error: 'a' was not declared in this scope
    4 |   vector<string> a(3);
      |                  ^
a.cc:6:5: error: 'cin' was not declared in this scope
    6 |     cin >> a[i];
      |     ^~~
a.cc:8:7: error: 'cout' was not declared in this scope
    8 |       cout << 'A';
      |       ^~~~
a.cc:11:7: error: 'cout' was not declared in this scope
   11 |       cout << 'B';
      |       ^~~~
a.cc:14:7: error: 'cout' was not declared in this scope
   14 |       cout << 'C';
      |       ^~~~
a.cc:17:7: error: 'cout' was not declared in this scope
   17 |       cout << 'D';
      |       ^~~~
a.cc:20:7: error: 'cout' was not declared in this scope
   20 |       cout << 'E';
      |       ^~~~
a.cc:23:7: error: 'cout' was not declared in this scope
   23 |       cout << 'F';
      |       ^~~~
a.cc:26:7: error: 'cout' was not declared in this scope
   26 |       cout << 'G';
      |       ^~~~
a.cc:29:7: error: 'cout' was not declared in this scope
   29 |       cout << 'H';
      |       ^~~~
a.cc:32:7: error: 'cout' was not declared in this scope
   32 |       cout << 'I';
      |       ^~~~
a.cc:35:7: error: 'cout' was not declared in this scope
   35 |       cout << 'J';
      |       ^~~~
a.cc:38:7: error: 'cout' was not declared in this scope
   38 |       cout << 'K';
      |       ^~~~
a.cc:41:7: error: 'cout' was not declared in this scope
   41 |       cout << 'M';
      |       ^~~~
a.cc:44:7: error: 'cout' was not declared in this scope
   44 |       cout << 'N';
      |       ^~~~
a.cc:47:7: error: 'cout' was not declared in this scope
   47 |       cout << 'O';
      |       ^~~~
a.cc:50:7: error: 'cout' was not declared in this scope
   50 |       cout << 'P';
      |       ^~~~
a.cc:53:7: error: 'cout' was not declared in this scope
   53 |       cout << 'Q';
      |       ^~~~
a.cc:56:7: error: 'cout' was not declared in this scope
   56 |       cout << 'R';
      |       ^~~~
a.cc:59:7: error: 'cout' was not declared in this scope
   59 |       cout << 'S';
      |       ^~~~
a.cc:62:7: error: 'cout' was not declared in this scope
   62 |       cout << 'T';
      |       ^~~~
a.cc:65:7: error: 'cout' was not declared in this scope
   65 |       cout << 'U';
      |       ^~~~
a.cc:68:7: error: 'cout' was not declared in this scope
   68 |       cout << 'V';
      |       ^~~~
a.cc:71:7: error: 'cout' was not declared in this scope
   71 |       cout << 'W';
      |       ^~~~
a.cc:74:7: error: 'cout' was not declared in this scope
   74 |       cout << 'X';
      |       ^~~~
a.cc:77:7: error: 'cout' was not declared in this scope
   77 |       cout << 'Y';
      |       ^~~~
a.cc:80:7: error: 'cout' was not declared in this scope
   80 |       cout << 'Z';
      |       ^~~~
a.cc:83:3: error: 'cout' was not declared in this scope
   83 |   cout << endl;
      |   ^~~~
a.cc:83:11: error: 'endl' was not declared in this scope
   83 |   cout << endl;
      |           ^~~~