coada2

#include <fstream>
#define LL long long int
using namespace std;

int main()
{
    LL x,y,z;
    ifstream f("coada2.in");
    f>>x>>y>>z;
    f.close();
    ofstream g("coada2.out");
    if(x>=y||x>=z)
        g<<-1;
    else
        g<<y+z-x;
    g.close();
    return 0;
}