Compilare: main.cpp: In function 'int main()': main.cpp:22:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s1.size(); i++) ~^~~~~~~~~~ main.cpp:36:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s2.size(); i++) ~^~~~~~~~~~ main.cpp:56:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s1.size(); i++) ~^~~~~~~~~~ main.cpp:70:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s2.size(); i++) ~^~~~~~~~~~ main.cpp:84:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s3.size(); i++) ~^~~~~~~~~~ main.cpp:104:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s1.size(); i++) ~^~~~~~~~~~ main.cpp:119:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s2.size(); i++) ~^~~~~~~~~~ main.cpp:133:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s3.size(); i++) ~^~~~~~~~~~ main.cpp:147:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s4.size(); i++) ~^~~~~~~~~~