#include <bits/stdc++.h> #include<iostream> #include<algorithm> #include<cstdlib> #include<cstring> #include<cstdio> #include<string> #include<vector> #include<bitset> #include<queue> #include<deque> #include<stack> #include<cmath> #include<list> #include<map> #include<set> //#define DEBUG #define RI register int using namespace std; typedef long long ll; //typedef __int128 lll; const int N=100000+10; const int M=100000+10; const int MOD=1e9+7; const double PI = acos(-1.0); const double EXP = 1E-8; const int INF = 0x3f3f3f3f; int t,n,m,k,q; int ans,cnt,flag,s,c,temp,sum; int a[N]; int b[N]; char str; struct node{}; int main() { #ifdef DEBUG freopen("input.in", "r", stdin); //freopen("output.out", "w", stdout); #endif //ios::sync_with_stdio(false); //cin.tie(0); //cout.tie(0); //scanf("%d",&t); //while(t--){ scanf("%d%d%d",&m,&s,&c); for(int i=1;i<=c;i++){ scanf("%d",&a[i]); } if(m>=c){ cout<<c<<endl; return 0; } sort(a+1,a+c+1); ans=a[c]-a[1]+1; for(int i=1;i<c;i++){ b[i]=a[i+1]-a[i]-1; } sort(b+1,b+c,greater<int>()); for(int i=1;i<m;i++){ ans-=b[i]; } cout<<ans<<endl; //}

#ifdef DEBUG printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC); #endif //cout << "Hello world!" << endl; return 0; }