就这么玄学的吗？下载数据，发现结果是对的，但是wa了

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<cctype>
using namespace std;

const int maxn = 2e5;
int a[maxn + 10];
char s[maxn];

int main() {
	freopen("input.txt", "r", stdin);
	
	scanf("%s", s);
	int len = strlen(s);
	a[0] = 0;
	
	int last = 0;
	for(int i = 0; i < len; i++) {
		if(isdigit(s[i])) {
			last = last * 10 + s[i] - '0';
			continue;
		}
		if(s[i] == '.') {
			a[++a[0]] = last;
			last = 0;
			continue;
		}
		if(s[i] == '-') {
			if(a[0] == 1) {
				a[1] = -a[1];
				continue;
			}
			a[--a[0]] = a[a[0]] - a[a[0] + 1];
			continue;
		}
		if(s[i] == '+') {
			if(a[0] == 1) {
				continue;
			}
			a[--a[0]] = a[a[0]] + a[a[0] + 1];
			continue;
		}
		if(s[i] == '*') {
			a[--a[0]] = a[a[0]] * a[a[0] + 1];
			continue;
		}
		if(s[i] == '/') {
			a[--a[0]] = a[a[0]] / a[a[0] + 1];
			continue;
		}
		if(s[i] == '@') break;
	}
	printf("%d\n", a[1]);
    return 0;
}