啊啊啊不会了

#include <bits/stdc++.h>

using namespace std;
int top, buttom;
int main(){
    //freopen(".in", "r", stdin);
    //freopen(".out", "w", stdout);
    string a;
    cin >> a;
    int Stack[10005] = {};
    for(int i = 0; i < a.length(); i++) {
        if(a[i] >= '0' && a[i] <= '9' && (i == 0 || a[i - 1] == '.')) {
            int c = 0, k = i;
            while(1) {
                if(a[k] == '.') {
                    break;
                }else{
                    int x = a[k] - '0';
                    c = c * 10 + x;
                    k++;
                }
            }
            Stack[top] = c;
            top++;
        }
        if(a[i] < '0' || a[i] > '9') {
            char x = a[i];
            if(x == '-') {
                int w = Stack[top - 2] - Stack[top - 1];
                top = top - 2;
                Stack[top] = w;
                top++;
            }
            if(x == '+') {
                int w = Stack[top - 2] + Stack[top - 1];
                top = top - 2;
                Stack[top] = w;
                top++;
            }
            if(x == '*') {
                int w = Stack[top - 2] * Stack[top - 1];
                top = top - 2;
                Stack[top] = w;
                top++;
            }
            if(x == '/') {
                int w = Stack[top - 2] / Stack[top - 1];
                top = top - 2;
                Stack[top] = w;
                top++;
            }
            if(x == '@') {
                cout << Stack[top - 1];
            }
        }

    }
    return 0;
}