foo.c: In function 'main':
foo.c:10:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ^~~~~~~~~~~~~~
foo.c:12:31: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         for(int j=0;j<=i;j++){scanf("%d",&a[i][j]);}
                               ^~~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。