Compilare: main.cpp: In function 'int main()': main.cpp:64:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (poz[i] < v[i].size () && v[i][poz[i]] <= nr) { ~~~~~~~^~~~~~~~~~~~~~ main.cpp: In function 'char next_ch()': main.cpp:17:29: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, DIM, fin); ^