/in/foo.c:3:1: error: unknown type name 'Void'
 Void Contact(int s1[],int s2[]);
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:7:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:8:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s2);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:9:10: warning: passing argument 1 of 'Contact' from incompatible pointer type [-Wincompatible-pointer-types]
  Contact(s1,s2);
          ^~
/in/foo.c:3:6: note: expected 'int *' but argument is of type 'char *'
 Void Contact(int s1[],int s2[]);
      ^~~~~~~
/in/foo.c:9:13: warning: passing argument 2 of 'Contact' from incompatible pointer type [-Wincompatible-pointer-types]
  Contact(s1,s2);
             ^~
/in/foo.c:3:6: note: expected 'int *' but argument is of type 'char *'
 Void Contact(int s1[],int s2[]);
      ^~~~~~~
/in/foo.c: At top level:
/in/foo.c:12:1: error: unknown type name 'Void'
 Void Contact(int s1[],int s2[])
 ^~~~
/in/foo.c: In function 'Contact':
/in/foo.c:15:15: warning: passing argument 1 of 'strlen' from incompatible pointer type [-Wincompatible-pointer-types]
   s1[i+strlen(s1)-1]=s2[i+1];
               ^~
In file included from /in/foo.c:2:0:
/usr/include/string.h:394:15: note: expected 'const char *' but argument is of type 'int *'
 extern size_t strlen (const char *__s)
               ^~~~~~
/in/foo.c:16:5: error: 'i' undeclared (first use in this function)
  s1[i+strlen(s1)-1]=0;
     ^
/in/foo.c:16:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:16:14: warning: passing argument 1 of 'strlen' from incompatible pointer type [-Wincompatible-pointer-types]
  s1[i+strlen(s1)-1]=0;
              ^~
In file included from /in/foo.c:2:0:
/usr/include/string.h:394:15: note: expected 'const char *' but argument is of type 'int *'
 extern size_t strlen (const char *__s)
               ^~~~~~
/in/foo.c:17:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^