/in/foo.c: In function 'main':
/in/foo.c:15:35: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   15 |                 if (str[i] >= 'A' && str[i] <= 'Z' || str[i] >= 'a' && str[i] <= 'z') {
      |                     ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
/in/foo.c:6:23: warning: unused variable 'f' [-Wunused-variable]
    6 |         char c = '\0',f,n;
      |                       ^