`121

#include <iostream>
using namespace std;

int a[21][21],n,i,j,s1,s2;
int main()
{cin>>n;
for(i=1;i<=n;i++)
    for(j=1;j<=n;j++)
    cin>>a[i][j];
for(i=2;i<=n;i++)
    for(j=1;j<=i-1;j++)
    s1+=a[i][j];
for(i=1;i<=n-1;i++)
    for(j=i+1;j<=n;j++)
    s2+=a[i][j];
while(s1!=s2)
    if(s1>s2)
    s1=s1-s2;
else
    s2=s2-s1;
cout<<s1;
}