foo.cc: In function 'int main()':
foo.cc:17:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d",&m,&n,&kk,&ll);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:21:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d",&t[i][j]);
             ~~~~~^~~~~~~~~~~~~~~

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