#include<bits/stdc++.h>
using namespace std;
int a[105][105];
int main(){
    int n;
    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++){
            if(a[i+1][j]>a[i+1][j+1]){
                a[i][j]=a[i][j]+a[i+1][j];
            }
            else
            {
                a[i][j]=a[i][j]+a[i+1][j+1];
            }
        }
    }
    cout<<a[1][1];
}


/**************************************************************
	Problem: 1216
	User: luyanchen
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2116 kb
****************************************************************/