Compilare: user.cpp: In function ‘void back(int, int)’: user.cpp:9:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[nr].size();i++){ ^ user.cpp: In function ‘int main()’: user.cpp:22:24: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d",&n); ^ user.cpp:25:35: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d",&val[i+1]); ^ user.cpp:29:33: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d%d",&a,&b); ^