memset(f, 0xc0, sizeof f)可以表示负无穷大，不需要用多重for循环去初始化

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 510;

int n;
int a[N][N];
int f[N][N];

int main(){
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= i; j++)
            scanf("%d", &a[i][j]);

    memset(f, 0xc0, sizeof f);

    f[1][1] = a[1][1];
    for(int i = 2; i <= n; i++)
        for(int j = 1; j <= i; j++)
            f[i][j] = max(f[i-1][j-1], f[i-1][j]) + a[i][j];

    int res = -1e8;
    for(int i = 1; i <= n; i++) res = max(res, f[n][i]);

    printf("%d", res);

    return 0;
}