#include <bits/stdc++.h>

using namespace std;
const int NMAX = 102;

ifstream fin("sumtri.in");
ofstream fout("sumtri.out");

int m[NMAX][NMAX], s[NMAX][NMAX];
int N, Max;

int read(){
    fin >> N;
    for(int i=0; i<N; i++){
        for(int j=0; j<N; j++){
            if(j<i+1){
                fin >> m[i][j];
                s[i][j] = max(s[i-1][j], s[i-1][j-1]) + m[i][j];
                Max = max(s[i][j], Max);
            } else
                m[i][j] = -1;
        }
    }
}

int main(){

    read();
    fout << Max;

    return 0;
}