#include #include #include #include #include #include #include #include #include #include #include using namespace std; #define ll long long #define INF (1 << 30) #define INFLL (1LL << 60) int main() { int a; cin >> a; if(a - 7 <= 0){ cout << -1 << endl; }else{ cout << a - 7 << endl; } return 0; }