#include <stdio.h>  // old io
#include <algorithm>
#include <ctype.h>  // tolower
inline bool lt_nocase(char c1, char c2) { return tolower(c1) < tolower(c2); }
using namespace std;
int main() 
{    
  char A[] = "fdBeACFDbEac";
  const int N = sizeof(A) - 1; 
  sort(A, A+N, lt_nocase); // same as stable_sort
  printf("%s\n", A);  
  // The printed result is ""AaBbCcdDeEfF" because sort is stable.
}