/in/foo.c: In function 'main':
/in/foo.c:19:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%s%s",s1+1,s2+1);
     ^~~~~
/in/foo.c:19:5: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:19:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:29:9: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
         printf("%d",c[i]);
         ^~~~~~
/in/foo.c:29:9: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:29:9: note: include '<stdio.h>' or provide a declaration of 'printf'