#include <stdio.h> #include <algorithm> #include <vector> #include <deque> #include <string> #include <iostream> using namespace std; using ll = long long; void solve(); int main() { solve(); #ifdef DBG while (true); #endif } //395 void solve() { int A; scanf("%d", &A); if (A < 15) printf("%d\n", -1); else printf("%d\n", A - 7); }