#include <bits/stdc++.h>
#define int long long
#define elif else if
#define fin(x) freopen (x,"r",stdin)
#define fout(x) freopen (x,"w",stdout)
#define rnt register int
#define reg(i,x,y) for (register int i=(x);i<=(y);++i)
#define Reg(i,x,y) for (register int i=(y);i>=(x);--i)
using namespace std;
namespace rwm {inline int read () {int s=0,w=0;char c=getchar ();while (!isdigit (c)){w|=(c=='-');c=getchar ();}while (isdigit (c)) {s=(s<<1)+(s<<3)+(c^48);c=getchar ();}return w?-s:s;}inline void write (int x) {if (x<0) putchar ( '-'),x=-x;if (x>9) write (x/10);putchar (x%10|48);}inline void writesp (int x) {write (x),putchar (' ');}inline void writeln (int x) {write (x),putchar ('\n');}inline int square (int x) {return x*x;}inline int floor (long double x) {return x;}inline int ceil (long double x) {return (int)(x+0.5);}inline int gcd (int x,int y) {int z=x%y;while (z) x=y,y=z,z=x%y;return y;}inline int lcm (int x,int y) {return x/gcd (x,y)*y;}};
using namespace rwm;
int n,ans,a[101][101],f[101][101];
signed main ()
{
	n=read ();
	reg (i,1,n)
		reg (j,1,i) a[i][j]=read ();
	reg (i,1,n)
		reg (j,1,i)
			f[i][j]=max (f[i-1][j],f[i-1][j-1])+a[i][j],ans=max (ans,f[i][j]);
	write (ans);
	return 0;
}