#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include <iomanip>
using namespace std;

int main(){
    int a, b, c, ans, cnt = 0;
    cin >> a >> b >> c;
    if (b >= c){
        ans = c;
        if (ans%a == 0) cout << ans/a << endl;
        else cnt--;
    }
    ans = c + b;
    if (ans%a == 0){
        cout << ans/a << endl;
        cnt++;
    }
    else cnt--;
    if (cnt < 0) cout << -1 << endl;
}