Main.c: In function ‘main’:
Main.c:5:2: error: variable-sized object may not be initialized
    5 |  int a[n+1][m+1]={0};
      |  ^~~
Main.c:7:10: warning: unused variable ‘v’ [-Wunused-variable]
    7 |  int x,y,v;
      |          ^
Main.c:7:8: warning: unused variable ‘y’ [-Wunused-variable]
    7 |  int x,y,v;
      |        ^
Main.c:7:6: warning: unused variable ‘x’ [-Wunused-variable]
    7 |  int x,y,v;
      |      ^