#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int N=20005;
int n,m;
int ans,a[N],sum[N];
int main()
{
	freopen("perfecttour.in","r",stdin);
	freopen("perfecttour.out","w",stdout);
	memset(a,0xcf,sizeof(a));
	scanf("%d%d",&n,&m);
	--m;
	int k;
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j)
			scanf("%d",&k),a[j]=max(a[j],k);
	int mn=0;
	for(int i=1;i<=m;++i) sum[i]=sum[i-1]+a[i];
	for(int i=1;i<=m;++i) ans=max(ans,sum[i]-mn),mn=min(sum[i],mn);
	printf("%d",ans);
	return 0;
}