plus.cpp: In function 'std::string adunare(std::string, std::string)': plus.cpp:9: warning: comparison between signed and unsigned integer expressions plus.cpp:11: warning: comparison between signed and unsigned integer expressions plus.cpp:12: warning: comparison between signed and unsigned integer expressions plus.cpp:17: warning: comparison between signed and unsigned integer expressions plus.cpp:19: warning: comparison between signed and unsigned integer expressions plus.cpp:20: warning: comparison between signed and unsigned integer expressions plus.cpp:28: warning: comparison between signed and unsigned integer expressions plus.cpp:30: warning: comparison between signed and unsigned integer expressions plus.cpp:31: warning: comparison between signed and unsigned integer expressions plus.cpp:37: warning: comparison between signed and unsigned integer expressions plus.cpp:53: warning: comparison between signed and unsigned integer expressions plus.cpp:55: warning: comparison between signed and unsigned integer expressions plus.cpp:56: warning: comparison between signed and unsigned integer expressions plus.cpp:62: warning: comparison between signed and unsigned integer expressions