Compilare: main.cpp: In function 'int main()': main.cpp:18:56: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(!ans.empty() &&ans.back()<s[i] &&ans.size()+n-i>m) ~~~~~~~~~~~~~~^~ main.cpp:23:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (ans.size()+n-i-1==m){ ~~~~~~~~~~~~~~~~^~~