/*
欧拉计划第81题， DP
answer: 427337
*/

#include<bits/stdc++.h>

using namespace std;

const int N = 1000;

int d[N][N];
int ans[N][N], n = 80;

int main(void)
{
    for (int i = 1; i <= n; ++ i)
        for (int j = 1; j <= n; ++ j)
        {
            cin >> d[i][j];

            if (i == 1) ans[i][j] = ans[i][j-1] + d[i][j];
            else
            {
                if (j == 1)
                {
                    ans[i][j] = ans[i-1][j] + d[i][j];
                }
                else
                {
                    ans[i][j] = min(ans[i-1][j], ans[i][j-1]) + d[i][j];
                }
            }
        }

    cout << ans[n][n] << endl;

    return 0;
}