1 #include 
     
       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             else40                 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 }