#include<iostream>
using namespace std;
int A[20][20];
int n,dis;
void dfs(int x,int y,int Curr){
if(x==n){
if(Curr>dis)dis=Curr;
return;
}
dfs(x+1,y,Curr+A[x+1][y]);
dfs(x+1,y+1,Curr+A[x+1][y+1]);
}
int main(){
int m;
cin>>m;
cin>>n;
for(int i=1;i<=n;i++)
for(int j=1;j<=i;j++)
cin>>A[i][j];
dis=0;
dfs(1,1,A[1][1]);
cout<<dis<<endl;
return 0;
}
