foo.cc: In function 'int main()':
foo.cc:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
foo.cc:27:84: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(int i = 1; i <= n; i++) for(int j = 1; j <= n; j++) scanf("%lld", &f[i][j]), b[i][j] = f[i][j];
                                                             ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:28:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d", &m, &frm, &to, &p);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

正在同步测试数据，请稍后
自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。