DP[i][j]=Max(DP[i-][j],DP[i-][j-])+a[i][j]

ans=Max(DP[n][..n])

#include <bits/stdc++.h>

#define Max(a,b) a>b?a:b

using namespace std;

typedef long long LL;

inline LL read() { LL x=; int f=; char ch=getchar();

    while(!isdigit(ch)) { if (ch=='-') f=-; ch=getchar();}

    while(isdigit(ch)) x=(x<<)+(x<<)+(ch^),ch=getchar(); return x*f;

}

int n;

const int N=<<;

LL a[N][N];

LL DP[N][N];

signed main(){

    n=read();

    for(register int i=;i<=n;i++)

    for(register int j=;j<=i;j++) a[i][j]=read();

    for(register int i=;i<=n;i++)

    for(register int j=;j<=i;j++) DP[i][j]=a[i][j],DP[i][j]+=Max(DP[i-][j],DP[i-][j-]);

    LL ans=-;

    for(register int i=;i<=n;i++) ans=Max(ans,DP[n][i]);

    cout << ans << endl ;

    return ;

}