纪念char n反向冲分

cf 1322A

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <iomanip>
#include <string>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <vector>
#include <map>

#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define ll long long
#define ull unsigned long long
#define uint unsigned int
#define l(x) ((x)<<1)
#define r(x) ((x)<<1|1)
#define lowbit(x) ((x)&(-(x)))
#define ms(a,b) memset(a,b,sizeof(a))
#define NSYNC std::ios::sync_with_stdio(false);std::cin.tie(0);std::cout.tie(0);

using namespace std;

char str[1111111];
int val,len, ans,n;

int main() {
	ans = val = len = 0;
	scanf("%d", &n);
	scanf("%s", str);

	for (int i = 0; i < n; i++) {
		len++;
		if (str[i] == '(') {
			val++;
			if (val == 0) {
				ans += len;
				len = 0;
			}
		}
		else val--;
		if (val == 0) len = 0;
	}

	if (val != 0) {
		printf("-1\n");
		return 0;
	}

	printf("%d\n", ans);

	return 0;
}