#include <cstdio>
using I = unsigned int;
static constexpr I MAXN=2000;
static I cnt[MAXN*MAXN];
static I calc() {
I N, K, v, ret;
scanf("%u %u", &N, &K);
for (I y=0; y<N; ++y) {
for (I x=0; x<=y; ++x) {
I c;
if (y == 0)
c = 1;
else if (y == 1)
c = 2;
else if (x == 0)
c = cnt[(y-1)*MAXN]+1;
else if (x == y)
c = cnt[(y-1)*MAXN+x-1]+1;
else
c = cnt[(y-1)*MAXN+x-1]+cnt[(y-1)*MAXN+x]-cnt[(y-2)*MAXN+x-1]+1;
cnt[y*MAXN+x] = c;
scanf("%u", &v);
if (c == 1)
ret = v;
else if (c <= K && v < ret)
ret = v;
}
}
return ret;
}
int main() {
printf("%d\n", calc());
return 0;
}