#include<bits/stdc++.h>
using namespace std;

int main(){
  int a,b,c;
  cin>>a>>b>>c;
  
  cout<<21-a-b-c<<endl;}
#include<bits/stdc++.h>
using namespace std;
typedef long long li;
typedef long double ld;
typedef pair<int,int> pt;
typedef pair<ld, ld> ptd;
typedef unsigned long long uli;

#define SORT(vec) sort(vec.begin(), vec.end())
#define loop(i,a,n) for(int i=a;i<n;i++)
#define pb push_back
#define mp make_pair
#define mset(a, val) memset(a, val, sizeof (a))
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define ft first
#define sc second
#define sz(a) int((a).size())
#define x first
#define y second


const int INF = int(1e9);
const li INF64 = li(INF) * li(INF);
const ld EPS = 1e-9;
const ld PI = ld(3.1415926535897932384626433832795);
int main(){
float x,y,z;
cin>>x>>y>>z;
int i=0;
while(1){
	if(float(y/x)<=float(i/z)){
		cout<<i-1;break;
	}
	i++;
}
return 0;
}
