//从上往下

#include <iostream>

#include <algorithm>

using namespace std;

const int N = , INF = 1e9;

int n;

int a[N][N];

int f[N][N];

int main() {

    scanf("%d", &n);

    for (int i = ; i <= n; i ++ )

        for (int j = ; j <= i; j ++ )

            scanf("%d", &a[i][j]);

    for (int i = ; i <= n; i ++ )

        //要初始化一个，比如这一行最后一个的右上没有，要初始化为负无穷

        for (int j = ; j <= i + ; j ++ )

            f[i][j] = -INF;

    f[][] = a[][];//

    for (int i = ; i <= n; i ++ )

        for (int j = ; j <= i; j ++ )

            f[i][j] = max(f[i - ][j - ] + a[i][j], f[i - ][j] + a[i][j]);

    int res = -INF;

    for (int i = ; i <= n; i ++ ) res = max(res, f[n][i]);//取最后一行的最大值

    printf("%d\n", res);

    return ;

}