Compilare: user.cpp: In function ‘int main()’: user.cpp:53:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<N[X[i]].size(); j++) ~^~~~~~~~~~~~~~~ user.cpp: In function ‘void nextS()’: user.cpp:17:25: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(S,1,100000,fi); ^