/in/lab4.c: In function 'f':
/in/lab4.c:81:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < strlen(str); i++) {
                           ^
/in/lab4.c: In function 'main':
/in/lab4.c:115:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0;i<strlen(str);i++){
                        ^