求hackABC423C（挂2点）

#include<bits/stdc++.h>
using namespace std;
#define int long long

const int N = 2e5+10;

int n,s;
int a[N];

signed main() {
	scanf("%lld%lld", &n,&s);
	for(int i=1;i<=n;i++) scanf("%lld", &a[i]);
	
	int l=1e9, r=0;
	for(int i=1;i<=n;i++)
		if(a[i] == 0)
			l = min(l, i),
			r = max(r, i);
			
	if(l == 1e9) {
		printf("0\n");
		return 0;
	}
	
	if(s < l) l = s+1;
	if(s > r) r = s-1;
	
	int ans = r-l+1;
	for(int i=l; i<=r; i++)
		if(a[i] == 1) ans++;
	
	printf("%lld\n", ans);
	
	return 0;
}