#include<bits/stdc++.h>

using namespace std;
typedef long long ll;
#define sz(s) (int)(s).size()
#define all(s) s.begin(),s.end()

void Speed() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
}

void solve() {
    int n,a,b;
    cin>>n>>a>>b;
    cout<<n-a-b;
}

int main() {
    Speed();
    int tc = 1;
    //cin >> tc;
    while (tc--) {
        solve();
    }
    return 0;
}