Compilare: main.cpp: In function 'int main()': main.cpp:39:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 39 | for (j = 0; j < s.length(); j++) { | ~~^~~~~~~~~~~~ main.cpp:32:19: warning: unused variable 'nr' [-Wunused-variable] 32 | int i, j, nr, c,n; | ^~