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#include <iostream>
#include <algorithm>
using namespace std;
int N,ans,a;
int dp[400][400];

int main(){
  //ios::sync_with_stdio(false);cin.tie(0);
  scanf("%d", &N);
  for(int i=0;i<N;i++)for(int j=0;j<=i;j++){
    scanf("%d", &a);
    dp[i][j] += a;
    ans = max(dp[i][j], ans);
    dp[i+1][j] = max(dp[i+1][j], dp[i][j]);
    dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j]);
  }
  printf("%d\n", ans);
}