Eroare de compilare: user.cpp: In function ‘void back(int)’: user.cpp:24:13: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(valid(k)) ^ user.cpp: At global scope: user.cpp:33:2: error: expected initializer before ‘cin’ cin>>N; ^ user.cpp:34:2: error: expected unqualified-id before ‘if’ if (N%2==1) ^ user.cpp:39:2: error: expected unqualified-id before ‘if’ if(n==18) ^ user.cpp:44:2: error: ‘n’ does not name a type n=2*N-1; ^ user.cpp:45:5: error: expected unqualified-id before ‘for’ for(i=4;i<=n;i=i+=2) ^ user.cpp:45:13: error: ‘i’ does not name a type for(i=4;i<=n;i=i+=2) ^ user.cpp:45:18: error: ‘i’ does not name a type for(i=4;i<=n;i=i+=2) ^ user.cpp:47:6: error: ‘r’ does not name a type r=sqrt(n); ^ user.cpp:48:5: error: expected unqualified-id before ‘for’ for(i=3; i<=r; i=i+2) ^ user.cpp:48:14: error: ‘i’ does not name a type for(i=3; i<=r; i=i+2) ^ user.cpp:48:20: error: ‘i’ does not name a type for(i=3; i<=r; i=i+2) ^ user.cpp:49:18: error: ‘j’ does not name a type for (j=i+i;j<=n;j=j+i) ^ user.cpp:49:23: error: ‘j’ does not name a type for (j=i+i;j<=n;j=j+i) ^ user.cpp:51:5: error: ‘a’ does not name a type a[1]=1; ^ user.cpp:52:9: error: expected constructor, destructor, or type conversion before ‘(’ token back(2); ^