为什么题目样例过了，第一个输入数据掏出来本地也过了，运行就是全WA？

#include <iostream>
#include <vector>
#include <string>
#include <cctype>
using namespace std;

int main() {
    int n;
    cin >> n;
    string s;
    cin >> s;

    cin.ignore();
    for (int i = 0; i < n; i++) {
        string line;
        getline(cin, line);
        int flag = line[0] - '0';
        if (flag == 1) {
            string str1;
            str1.assign(line, 2, line.size());
            s += str1;
            cout << s << endl;
        } else if (flag == 2) {
            int j = 2;
            string strx = "";
            string stry = "";
            while (line[j] != ' ') {
                strx += line[j];
                j++;
            }
            while (j < line.size()) {
                stry += line[j];
                j++;
            }
            int a = stoi(strx);
            int b = stoi(stry);
            string str2;
            str2.assign(s, a, b);
            s = str2;
            cout << s << endl;
        } else if (flag == 3) {
            int j = 2;
            string strx = "";
            string stry = "";
            while (line[j] != ' ') {
                strx += line[j];
                j++;
            }
            j++; 
            while (j < line.size()) {
                stry += line[j];
                j++;
            }
            int x = stoi(strx);
            s.insert(x, stry);
            cout << s << endl;
        } else if (flag == 4) {
            string str4;
            str4.assign(line, 2, line.size());
            if (s.find(str4) != string::npos) {
                cout << s.find(str4) << endl;
            } else {
                cout << -1 << endl;
            }
        }
    }
    return 0;
}