/in/foo.c:1:11: error: 'N' undeclared here (not in a function)
 int prime[N*5000];
           ^
/in/foo.c: In function 'init':
/in/foo.c:8:5: warning: implicit declaration of function 'fill' [-Wimplicit-function-declaration]
     fill(phi,phi+5000001,1);
     ^~~~
/in/foo.c:10:5: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
     memset(isPrime,0,sizeof(isPrime));
     ^~~~~~
/in/foo.c:10:5: warning: incompatible implicit declaration of built-in function 'memset'
/in/foo.c:10:5: note: include '<string.h>' or provide a declaration of 'memset'
/in/foo.c:17:17: error: 'LL' undeclared (first use in this function)
             if((LL)i*(LL)prime[j]>5000000) break;
                 ^~
/in/foo.c:17:17: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:17:20: error: expected ')' before 'i'
             if((LL)i*(LL)prime[j]>5000000) break;
                    ^