Compilare: main.cpp: In function 'int main()': main.cpp:58:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int len = 1; len <= input.size(); len++) ~~~~^~~~~~~~~~~~~~~ main.cpp:67:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = len; i < input.size(); i++) ~~^~~~~~~~~~~~~~ main.cpp: In function 'int toNumber(char)': main.cpp:24:1: warning: control reaches end of non-void function [-Wreturn-type] } ^