/*
TASK:apple
LANG:C++
*/

#include<stdio.h>
#include<iostream>
using namespace std;
int mm[70][70],n,m,;
int k,f,br;
void cmp()
{while (1)
{br+=mm[k][f];
mm[k][f]=0;
if(k==n&&f==m) break;
 if (k==n) f++;
    else if (mm[k][f+1]>mm[k+1][f]) f++;
       else k++;
}
}
int main()
{cin>>n>>m;
for (int i=1;i<=n;i++)
    for (int j=1;j<=m;j++)
        cin>>mm[i][j];
for (int i=0;i<=n+1;i++)
    mm[i][m+1]=-1;
for (int i=0;i<=m+1;i++)
    mm[n+1][i]=-1;
k=f=1;
cmp();
k=f=1;
cmp();
  cout<<br<<"\n";  
 return 0;   
}
