#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll N, M, mi=0, mi2;
    cin >> N >> M;
    vector<vector<ll>> dp(N+1, vector<ll>(M+1, 1e18)), A(N+1, vector<ll>(M+1));
    for (int i=1; i<=N; i++){
        for (int j=1; j<=M; j++) cin >> A[i][j];
    }
    if (N == 1){
        cout << 0 << endl;
        return 0;
    }

    for (int i=2; i<=N; i++){
        mi2 = 1e18;
        for (int j=1; j<=M; j++){
            dp[i][j] = min(dp[i-1][j]+A[i][j], mi+A[i][j]+A[i-1][j]);
            mi2 = min(mi2, dp[i][j]);
        }
        swap(mi2, mi);
    }

    cout << mi << endl;

    return 0;
}