#include <iostream>
using namespace std;
int
g[101][101], ans[101][101], n;
void
__read__()
{
cin >> n;
for( int i = 1; i <= n; i++ )
for( int j = 1; j <= i; j++ )
cin >> g[i][j];
}
void
__dp__()
{
for( int i = 1; i <= n; i++ )
for( int j = 1; j <= i; j++ )
if( ans[i - 1][j] > ans[i - 1][j - 1] )
ans[i][j] = ans[i - 1][j] + g[i][j];
else
ans[i][j] = ans[i - 1][j - 1] + g[i][j];
}
void
__outp__()
{
int max = 0;
for( int i = 1; i <= n; i++ )
if( max < ans[n][i] )
max = ans[n][i];
cout << max << endl;
}
int
main()
{
__read__();
__dp__();
__outp__();
return 0;
}