#include<bits/stdc++.h>
using namespace std;
int n,a[105][105],dp[105][105];
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=i;j++){
            cin>>a[i][j];
            if(i==n) dp[i][j]=a[i][j];
        }
    }
    for(int i=n-1;i>=1;i--){
        for(int j=1;j<=n;j++){
            dp[i][j]=max(dp[i+1][j],dp[i+1][j+1])+a[i][j];
        }
    }
    cout<<dp[1][1];
}
/**************************************************************
	Problem: 1216
	User: zhangzekai
	Language: C++
	Result: Accepted
	Time:19 ms
	Memory:2160 kb
****************************************************************/