Compilare: main.cpp: In function 'int main()': main.cpp:18:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=2;i<a.length();i++) { ~^~~~~~~~~~~ main.cpp:30:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<b.length();i++) { ~^~~~~~~~~~~ main.cpp:35:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==a.length()-1) { ~^~~~~~~~~~~~~~