Compilare: main.cpp: In function 'int main()': main.cpp:12:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i + 1 < str.length(); ++i) { ~~~~~~^~~~~~~~~~~~~~ main.cpp:20:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < str.length(); ++j) ~~^~~~~~~~~~~~~~ main.cpp:5:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("gap.in", "r", stdin); ^ main.cpp:6:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("gap.out", "w", stdout); ^