Compilare: user.cpp: In function ‘int main()’: user.cpp:32:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(S.size()<K) ^ user.cpp:19:27: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&N,&K); ^ user.cpp:21:29: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] {fscanf(f,"%d %d",&x,&y);E[2*i-1]=make_pair(x,make_pair(1,i));E[2*i]=make_pair(y,make_pair(-1,i));} ^