#include <iostream>
using namespace std;
int n,i,j;
int a[101][101]={0};
int main(){
    cin>>n;
    for(i = 0;i < n;i++){
        for(j = 0;j <= i;j++){
            cin>>a[i][j];
        } 
    } 
    for(i = n - 2;i >= 0;i--){
        for(j = 0;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[0][0]<<endl;
    return 0;
}
 
/**************************************************************
	Problem: 1216
	User: liyunshuo
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2112 kb
****************************************************************/