Compilare: main.cpp: In function 'void build_pi(int*, const string&)': main.cpp:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int n = 2; n <= A.length(); n++) { ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:43:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int n = 0; n < B.length(); n++) { ~~^~~~~~~~~~~~ main.cpp:48:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == A.length()) { ~~^~~~~~~~~~~~~