#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n,m,i,j,a[11][11],b[11][11],s=0; cin>>n; for(i=1;i<=n;i++){ for(j=1;j<=n;j++){ cin>>a[i][j]; } } for(i=1;i<=n;i++){ for(j=1;j<=n;j++){ if(i+j==n+1||i==j){ s+=a[i][j]; } } } cout<<s; return 0; }