Compilare: main.cpp: In function 'int main()': main.cpp:70:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < prime.size() && prime[j] * prime[j] <= x; j++) { ~~^~~~~~~~~~~~~~ main.cpp: In function 'char next_ch()': main.cpp:31:31: 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, stdin); ^ main.cpp: In function 'int main()': main.cpp:54:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("deletegcd.in", "r", stdin); ^ main.cpp:55:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("deletegcd.out", "w", stdout); ^