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#include <bits/stdc++.h>
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using namespace std;
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const int N = 510;
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const int INF = 0x3f3f3f3f;
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int f[N][N];
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int a[N][N];
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int main() {
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int n;
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cin >> n;
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for (int i = 1; i <= n; i++)
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for (int j = 1; j <= i; j++)
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cin >> a[i][j];
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memset(f, -0x3f, sizeof f); // 预求最大，先设最小
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// 其实自上而下版本之所以需要初始化-INF，是因为每个枚举到的位置需要从它头顶和它的左上侧取值对比
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// 而它的正上方可能是不存在的，如果不初始化，就是0
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// 本题数据还可能是负数，就会造成它可会从正上方取来一个0做为最大值，造成结果错误
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f[1][1] = a[1][1];
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for (int i = 2; i <= n; i++)
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for (int j = 1; j <= i; j++)
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f[i][j] = max(f[i - 1][j - 1], f[i - 1][j]) + a[i][j];
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int res = -INF;
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for (int i = 1; i <= n; i++) res = max(res, f[n][i]);
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printf("%d\n", res);
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return 0;
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}
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