Compilare: main.c: In function 'main': main.c:14:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("sortnet.in","r",stdin),freopen("sortnet.out","w",stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:14:37: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("sortnet.in","r",stdin),freopen("sortnet.out","w",stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:15:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^~~~~~~~~~~~~~~~~~~ main.c:18:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf(" <%d ,%d >",&l,&h),--l,--h,a[i][l].u=h,a[i][h].u=l; ^~~~~~~~~~~~~~~~~~~~~~~~~