usaco-practice/codeforces/Caps Lock/index.cpp

#include <iostream>
#include <string>
using namespace std;

string parseString(string n) {
  string m = n;
  string o = n;
  for (int i = 0; i < n.length(); i++) {
    m[i] = toupper(n[i]);
  }
  o = m;
  o[0] = tolower(m[0]);
  if (m == n) {
    return "v1";
  } else if (o == n) {
    return "v2";
  } else {
    return "v3";
  }
}

int main() {
  string n;
  cin >> n;
  string w;
  w = parseString(n);
  if (w == "v3") {
    cout << n << endl;
  } else {
    for (int i = 0; i < n.length(); i++) {
      if (i == 0 && w == "v2") {
        n[0] = toupper(n[0]);
      } else {
        n[i] = tolower(n[i]);
      }
    }
    cout << n << endl;
  }
}