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#include <cstdio>
#include <cstring>
#include <cmath>
#include <cassert>
#include <iostream>
#include <algorithm>
#include <iterator>
#include <string>
#include <vector>
#include <queue>
#include <bitset>
#include <utility>
#include <stack>

using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
typedef vector<int> VI;
#define MP make_pair
#define FOR(v,p,k) for(int v=(p);v<=(k);++v)
#define FORD(v,p,k) for(int v=(p);v>=(k);--v)
#define REP(i,n) for(int i=0;i<(n);++i)
#define VAR(v,i) __typeof(i) v=(i)
#define FOREACH(i,c) for(VAR(i,(c).begin());i!=(c).end();++i)
#define PB push_back
#define ST first
#define ND second
#define SIZE(x) (int)x.size()
#define ALL(c) c.begin(),c.end()

#define ODD(x) ((x)%2)
#define EVEN(x) (!(ODD(x)))


int main() {
    VI curr, prev, prev2;
    int n, k;
    scanf("%d%d", &n, &k);

    curr.reserve(n+2);
    prev.reserve(n+2);
    prev2.reserve(n+2);
    prev2.PB(0);
    prev.PB(0);
    prev.PB(0);

    int res = 2000000000;
    FOR(i,1,n) {
        curr.PB(0);
        FOR(j,1,i) {
            int w;
            scanf("%d", &w);
            int min_to_remove = prev[j-1]+prev[j]-prev2[j-1]+1;
            curr.PB(min_to_remove);
            if (min_to_remove <= k) {
                res=min(res, w);
            }
        }
        curr.PB(0);

        swap(prev2, prev);
        swap(prev, curr);
        curr.clear();
    }
    printf("%d\n", res);
    return 0;
}