/in/foo.c: In function 'main':
/in/foo.c:8:16: warning: 'i' is used uninitialized [-Wuninitialized]
    8 |         a[i][1]=1;
      |         ~~~~~~~^~
/in/foo.c:5:11: note: 'i' was declared here
    5 |     int n,i,j;
      |           ^