原题链接：
https://www.acwing.com/problem/content/900/

#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
typedef long long ll;
int s[505][505];

int main()
{
    int n;
    cin >> n;
    cin >> s[0][0];
    for( int i=1;i<n;i++ )
    {
        cin >> s[i][0];
        s[i][0] += s[i-1][0] ;
        for( int j=1;j<i;j++ )
        {
            cin >> s[i][j];
            if( s[i-1][j-1] > s[i-1][j] ) s[i][j]+=s[i-1][j-1];
            else s[i][j]+=s[i-1][j];
        }
        cin >> s[i][i];
        s[i][i] += s[i-1][i-1];
    }
    int max=s[n-1][0];
    for ( int i=0;i<n;i++ ) if( max < s[n-1][i] ) max=s[n-1][i];
    cout << max;
}