foo.cc: In function 'int main()':
foo.cc:4:34: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
     for(scanf("%d",&n),f[i=1][j=n+1>>1]=1;k<=n*n;f[i][j]=k++)
                                 ~^~
foo.cc:4:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(scanf("%d",&n),f[i=1][j=n+1>>1]=1;k<=n*n;f[i][j]=k++)
         ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~