基因研究

**太难了太简单了

#include<bits/stdc++.h>
using namespace std;
long long s;
int main(){
    //freopen("s.in","r",stdin);
    //freopen("s.out","w",stdout);
    int n,k;
    scanf("%d%d",&n,&k);
    long long a[n];
    for(int i=0;i<n;i++){
        scanf("%lld",&a[i]);
        if(i==k-1){
            a[i]=0-a[i];
        }s+=a[i];
    }cout<<s;
    return 0;
}