#include<iostream>
#include<iomanip>
#include<cmath>
#include<string>
#include<cstring>
#include<vector>
#include<list>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<stack>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define mp make_pair
#define rep(i, n) for(int i=0;i<n;++i)
#define rrep(i, n) for(int i=n;i>=0;--i)
const int inf=1e9+7;
const ll mod=1e9+7;
const ll mod1=998244353;
const ll big=1e18;
const double PI=2*asin(1);

int main() {
  int N, M;
  cin>>N>>M;
  ll tmpA[N][M];
  for(int i=0;i<N;++i) {
    for(int j=0;j<M;++j) {
      cin>>tmpA[i][j];
    }
  }
  vector<ll> A(N);
  for(int i=0;i<N;++i) {
    A[i] = 0;
    for(int j=0;j<M;++j) {
      A[i] += tmpA[i][j];
    }
  }
  if(N==1) {
    cout<<A[0]<<endl;
    return 0;
  }
  bool up;
  ll ans = 0;
  if(A[0]<=A[1]) up = true;
  else {
    up = false;
    ans += A[0];
  }
  for(int i=1;i<N;++i) {
    if(up) {
      if(A[i]>A[i+1]) {
        up = false;
        ans += A[i];
      }
    }
    else {
      if(A[i]<A[i+1]) {
        up = true;
        ans -= A[i];
      }
    }
  }
  if(up) ans += A[N-1];
  cout<<ans<<endl;
}