993 992 991
 100 1 10
 960 935 994
 99 8 99
 60 16 1
 759 10 258
 24 19 9
 196 169 144
 1000 999 1
 945 812 917
 1000 100 10
 500 300 300
 888 777 1000
 2 1 4
 24 12 12
 767 2 514
 2 1 2
 1000 1 1
 5 2 1
 70 32 1
 765 123 899
 17 7 10
 5 4 10
 888 777 888
 66 38 4
 1000 999 1000
 9 3 300
 244 87 4
 765 123 45
 1000 1 1000
 305 203 421
 100 10 1
 64 12 8
 894 1 999
 2 1 1
 18 14 10
 6 2 4
 888 777 1
 27 26 1
 2 1 3
 5 1 5
 7 3 200
 561 31 917
 17 10 7
 93 74 831

1
 990
 27
 1127
 3
 19325
 3
 24
 1
 151
 90
 200
 143
 4
 12
 196605
 2
 999
 2
 2
 4693
 15
 3
 127
 3
 2
 600
 8
 235
 999000
 212
 9
 35
 892107
 1
 3
 8
 1
 1
 3
 20
 267
 15678
 5
 214

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,fma,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 
//ordered_set  
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 

#define ook order_of_key
#define fbo find_by_order
  
#define ll long long
#define ld long double
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define um unordered_map<ll, ll>
#define us unordered_set<ll>
#define SORT(v) sort(v.begin(),v.end())
#define fori(i,a,b) for(ll i=a;i<b;i++)
#define ford(i,a,b) for(ll i=a;i>=b;i--)
#define tc ll t;cin>>t;while(t--)
#define in_range(x, y, r, c) (x < r && y < c && x >= 0 && y >= 0)

#define MOD 1000000007
#define INF LLONG_MAX
#define PI 3.1415926535897932385

typedef pair<ll, ll> ii;
typedef pair<ii, ll> iii;
typedef vector<ii> vii;
typedef vector<ll> vi;
typedef vector<vector<ll>> vvi;

bool sortcol( const vector<ll>& v1, 
               const vector<ll>& v2 ) { 
 return v1[1] < v2[1]; 
} 

struct comparator{
    bool operator()( const ll &lhs,const ll &rhs)const{
        return lhs<rhs;
    }
};


/*
vi parent;
vi renk;
void initialise(){
    fori(i,1,n+1){parent[i]=i;}
    fori(i,1,n+1){renk[i]=1LL;}
}

ll find_set(ll p){
    if(parent[p]==p) return p;
    
    return parent[p]=find_set(parent[p]);
}

void set_union(ll x,ll y){
    ll a=find_set(x);
    ll b=find_set(y);
    if(a!=b){
        if(renk[a]<renk[b])
            swap(a,b);
        
        parent[b]=a;
        renk[a]+=renk[b];
    }
}
*/
ll a,b,c;ll td;
ll bn(ll l,ll r){
    
    if(l<=r){
        ll m= (l+r)/2;
        
        ll v= m*b;
        
        if(ceil((double)(td-v)/(double)b)==c)return m;
        
        if(ceil((double)(td-v)/(double)b)<c){
            return bn(l,m-1);
        }
        else return bn(m+1,r);
        
        
    }
    return -1;
}





int main() {
	ios_base::sync_with_stdio(false);cin.tie(NULL);
	cin>>a>>b>>c;
	
	td=a*c;
	
	cout<<bn(0,1000);
	
	
	
	
	return 0;
}
