Compilare: main.cpp: In function 'int main()': main.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<strlen(s)-1; i=i++) ~^~~~~~~~~~~~ main.cpp:15:38: warning: operation on 'i' may be undefined [-Wsequence-point] for(int i=1; i<strlen(s)-1; i=i++) ~^~~~