#include <iostream>

using namespace std;

int a;
const int N = 1100;
int x[N][N],y[N][N];


int main(){
    cin >> a;
    for (int i = 1; i <= a; i ++ ) {
        for (int j = 1; j <= i; j ++ ) cin >> x[i][j];
    }
    for (int i = 0; i <= a; i ++ ){
        for (int j = 0; j <= i + 1; j ++ ) {
            y[i][j] = -1e9;
        }
    }
    y[1][1] = x[1][1];
    for (int i = 2; i <= a; i ++ ){
        for (int j = 1;j <= i; j ++ ){
            y[i][j] = max(y[i - 1][j - 1] + x[i][j] ,y[i - 1][j] + x[i][j]);
        }
    }
    int l = -1e9;
    for (int i = 1; i <= a; i ++ ) l = max(l,y[a][i]);
    cout << l;
}