Compilare: main.cpp: In function 'int main()': main.cpp:72:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; ok == 0 && k < vec[a[i]].size(); k++) { ~~^~~~~~~~~~~~~~~~~~ main.cpp:52:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("showroom.in", "r", stdin); ^ main.cpp:53:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("showroom.out", "w", stdout); ^ main.cpp:59:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%c", &ch); ^ main.cpp:63:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%c", &ch); ^