Compilare: main.cpp: In function 'int main()': main.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<a.size(); i++) ~^~~~~~~~~ main.cpp:38:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<b.size(); j++) ~^~~~~~~~~ main.cpp:41:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0; k<c.size(); k++) ~^~~~~~~~~ main.cpp:44:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==a.size() && j==b.size() && k==c.size()) ~^~~~~~~~~~ main.cpp:44:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==a.size() && j==b.size() && k==c.size()) ~^~~~~~~~~~ main.cpp:44:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==a.size() && j==b.size() && k==c.size()) ~^~~~~~~~~~ main.cpp:28:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("base3.out","w",stdout); ^