Compilare: user.cpp: In function ‘int cal(int)’: user.cpp:31:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < prime.size() ; i++){ ^ user.cpp: At global scope: user.cpp:49:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main(){ ^ user.cpp: In function ‘int main()’: user.cpp:50:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cntgcd.in","r",stdin); ^ user.cpp:51:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cntgcd.out","w",stdout); ^