/in/foo.c: In function 'Merge':
/in/foo.c:17:3: warning: statement with no effect [-Wunused-value]
   for(j;j<n2;j++){
   ^~~
/in/foo.c:22:3: warning: statement with no effect [-Wunused-value]
   for(i;i<n1;i++){
   ^~~
/in/foo.c: In function 'main':
/in/foo.c:29:50: warning: unused variable 'j' [-Wunused-variable]
  int a1[10000]={0},a2[10000]={0},a3[10000]={0},i,j,n1,n2,n3;
                                                  ^