#include<bits/stdc++.h>
using namespace std;
int a[200][200];
int n;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=i;j++){
        cin>>a[i][j];
    }
    }
    for(int i=n-1;i>=1;i--){
        for(int j=1;j<=i;j++){
        a[i][j]=max(a[i+1][j],a[i+1][j+1])+a[i][j];
        //cout<<a[i][j]<<" "<<a[i-1][j]<<" "<<a[i-1][j-1]<<endl;
    }
    }
cout<<a[1][1];
    return 0;
}
/**************************************************************
	Problem: 1216
	User: zhangzekai
	Language: C++
	Result: Accepted
	Time:23 ms
	Memory:2228 kb
****************************************************************/