./Main.c:1:1: warning: data definition has no type or storage class
n;a[9][9];v[9];i;x,y;d(c,u,s,i){v[c]=1;for(i=0;i++<n;)s+=a[c][i]&!v[i]?d(i,u+1,0):0;v[c]=0;return u==n?:s;}main(m){for(scanf("%d%d",&n,&m);i++<m;)scanf("%d%d",&x,&y),a[x][y]=a[y][x]=1;printf("%d",d(1,1,0));}
^
./Main.c:1:1: warning: type defaults to ‘int’ in declaration of ‘n’ [-Wimplicit-int]
./Main.c:1:3: warning: data definition has no type or storage class
n;a[9][9];v[9];i;x,y;d(c,u,s,i){v[c]=1;for(i=0;i++<n;)s+=a[c][i]&!v[i]?d(i,u+1,0):0;v[c]=0;return u==n?:s;}main(m){for(scanf("%d%d",&n,&m);i++<m;)scanf("%d%d",&x,&y),a[x][y]=a[y][x]=1;printf("%d",d(1,1,0));}
^
./Main.c:1:3: warning: type defaults to ‘int’ in declaration of ‘a’ [-Wimplicit-int]
./Main.c:1:11: warning: data definition has no type or storage class
n;a[9][9];v[9];i;x,y;d(c,u,s,i){v[c]=1;for(i=0;i++<n;)s+=a[c][i]&!v[i]?d(i,u+1,0):0;v[c]=0;return u==n?:s;}main(m){for(scanf("%d%d",&n,&m);i++<m;)scanf("%d%d",&x,&y),a[x][y]=a[y][x]=1;printf("%d",d(1,1,0));}
^
....