Compilare: main.cpp: In function 'void df(int)': main.cpp:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<a[k].size();i++) { ~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:38:11: warning: unused variable 'j' [-Wunused-variable] int i,j,x,y; ^ main.cpp:39:27: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&n,&m); ^ main.cpp:41:31: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&x,&y); ^