Main.cc: In function ‘int main()’:
Main.cc:5:24: error: ‘N’ was not declared in this scope
int i, j, n, k = 1, a[N][N];
^
Main.cc:10:4: error: ‘a’ was not declared in this scope
a[i][j] = k++;
^
Main.cc:12:4: error: ‘a’ was not declared in this scope
a[j][n - i - 1] = k++;
^
Main.cc:14:4: error: ‘a’ was not declared in this scope
a[n - i - 1][j] = k++;
^
Main.cc:16:4: error: ‘a’ was not declared in this scope
a[j][i] = k++;
^
Main.cc:21:18: error: ‘a’ was not declared in this scope
printf("%5d", a[i][j]);
^
Main.cc:6:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~