1 #include <bits/stdc++.h>
2 #define _for(i,a,b) for(int i = (a);i < b;i ++)
3 typedef long long ll;
4 using namespace std;
5 int rnt = 0;
6 int N;
7 inline ll read()
8 {
9 ll ans = 0;
10 char ch = getchar(), last = ' ';
11 while(!isdigit(ch)) last = ch, ch = getchar();
12 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
13 if(last == '-') ans = -ans;
14 return ans;
15 }
16 inline void write(ll x)
17 {
18 if(x < 0) x = -x, putchar('-');
19 if(x >= 10) write(x / 10);
20 putchar(x % 10 + '0');
21 }
22
23 int main()
24 {
25 N = read();
26 int dp[2][N];
27 memset(dp,0,sizeof(dp));
28 dp[0][0] = read();
29 int rnt = 0;
30 _for(i,1,N)
31 {
32 _for(j,0,i+1)
33 {
34 int tmp = read();
35 if(j==0)
36 dp[i&0x1][j] = dp[!(i&0x1)][j] + tmp;
37 else if(j==i)
38 dp[i&0x1][j] = dp[!(i&0x1)][j-1] + tmp;
39 else
40 dp[i&0x1][j] = tmp + max(dp[!(i&0x1)][j],dp[!(i&0x1)][j-1]);
41 }
42 }
43
44 _for(i,0,N)
45 rnt = max(rnt,dp[!(N&0x1)][i]);
46 write(rnt);
47 return 0;
48 }
