Compilare: main.cpp: In function 'int main()': main.cpp:42:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 1 ; j <= (working.size() - 1) / 2 ; j++){ ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:15:18: warning: unused variable 'second' [-Wunused-variable] int i,first, second, it, j; ^~~~~~ main.cpp:15:26: warning: unused variable 'it' [-Wunused-variable] int i,first, second, it, j; ^~