Compilare: main.cpp: In function 'int main()': main.cpp:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= a.size() - 1; i++) { ~~^~~~~~~~~~~~~~~ main.cpp:32:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) { ~~^~~~~~~~~~ main.cpp:41:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = a.size(); i < b.size(); i++) { ~~^~~~~~~~~~ main.cpp:21:21: warning: unused variable 'P2' [-Wunused-variable] long long P1 = 1, P2 = 1, P3 = 1; ^~