#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int h, w;
    cin >> h >> w;
    if(h == 1){
        cout << 0 << '\n';
        return 0;
    }
    vector<vector<ll>> A(h, vector<ll>(w)), dp(h, vector<ll>(w));
    for(int y = 0; y < h; y++){
        for(int x = 0; x < w; x++){
            cin >> A[y][x];
        }
    }
    dp[0] = A[0];
    for(int y = 0; y + 1 < h; y++){
        ll v = *min_element(dp[y].begin(), dp[y].end());
        for(int x = 0; x < w; x++){
            dp[y + 1][x] = min(dp[y][x] + A[y + 1][x], A[y][x] + A[y + 1][x] + v);
        }
    }
    cout << *min_element(dp[h - 1].begin(), dp[h - 1].end()) << '\n';
}