#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<queue>
#include<cmath>
#include<algorithm>
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
long long  n,a[40000][40000],maxx=0x7fffffff; 
int main(){
	cin >>n;
	for(long long  i=1;i<=n;i++){
		for(long long  j=1;j<=n;j++){
			cin >>a[i][j];
		}	
	}
	long long  l=0;
	for(long long  i=1;i<=n;i++){
		long long  minn=0x7fffffff;
		for(long long  j=1;j<i;j++){
			if(a[i][j]<minn)minn=a[i][j];
		}
		if(minn!=0x7fffffff)l+=minn;
		
	}
	cout <<l;
	return 0;
}