foo.cc: In function 'int main()':
foo.cc:4:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n);
 ~~~~~^~~~~~~~~
foo.cc:6:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 for(int j=1;j<=i;j++) scanf("%d",&a[i][j]);
                       ~~~~~^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务