#include <bits/stdc++.h>

using namespace std;
const int NMAX = 102;

int N, Max = -(1 << 19);
int tri[NMAX][NMAX], s[NMAX][NMAX];

int main(){

    freopen("sumtri.in", "r", stdin);
    freopen("sumtri.out", "w", stdout);

    scanf("%d", &N);
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            if(j < i + 1){
                scanf("%d", &tri[i][j]);
                s[i][j] = max(s[i - 1][j - 1], s[i - 1][j]) + tri[i][j];
                Max = max(Max, s[i][j]);
            }
        }
    }

    printf("%d", Max);

    return 0;
}