Compilare: main.cpp: In function 'bool compare()': main.cpp:19:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i < n1.size();++i) ~~^~~~~~~~~~~ main.cpp: In function 'void multiply()': main.cpp:53:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i <= n1.size() + n2.size();++i) ~~^~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:56:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1;i <= n1.size();++i) ~~^~~~~~~~~~~~ main.cpp:57:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 1;j <= n2.size();++j) ~~^~~~~~~~~~~~ main.cpp: In function 'bool compare()': main.cpp:22:1: warning: control reaches end of non-void function [-Wreturn-type] } ^