#include<bits/stdc++.h>
using namespace std;
int a[200][200];
int n;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=i;j++){
		cin>>a[i][j];
	}
	}
	for(int i=n-1;i>=1;i--){
		for(int j=1;j<=i;j++){
		a[i][j]=max(a[i+1][j],a[i+1][j+1])+a[i][j];
		//cout<<a[i][j]<<" "<<a[i-1][j]<<" "<<a[i-1][j-1]<<endl;
	}
	}
cout<<a[1][1];
	return 0;
}

/**************************************************************
	Problem: 1216
	User: chenyubo
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2228 kb
****************************************************************/