#include <stdio.h>
int main() {
    int m, n;
    scanf("%d %d", &m, &n);
    if(m < 0 || n < 0) {
        printf("-1");
        return 0;
    }
    int a[100][100];
    for(int i = 0; i < m; i++) {
        for(int j = 0; j < n; j++) {
            scanf("%d", &a[i][j]);
        }
    }
    int top = 0, bottom = m - 1;
    int left = 0, right = n - 1;
    while(top <=bottom && left <= right) {
        for(int i = left; i <= right; i++)
        printf("%d", a[top][i]);
    top++;
    for(int i = top; i <= bottom; i++)
        printf("%d", a[i][right]);
    right--;
    if(top <= bottom) {
        for(int i = right; i >= left; i--)
    printf();
    }
    
    }
    return 0;
}