2那个点不会做，用substr第3个点又出问题了，求救！

#include<bits/stdc++.h>
using namespace std;
string s,m,d,f;
string a1[105];
int a2[105];
int main(){
	int z=1;
	char t;
	int n,a,b,c;
	cin>>n>>s;
	for(int i=1;i<=n;i++){
		cin>>t;
		if(t=='1'){
			cin>>m;
			s=s+m;
			a1[z]=s;
			z++;
		}
		if(t=='2'){
			cin>>a>>b;
			s.erase(0,a);
			a1[z]=s;
			z++;
		}
		if(t=='3'){
			cin>>c>>d;
			s.insert(c,d);
			a1[z]=s;
			z++;
		}
		if(t=='4'){
			cin>>f;
			if(s.find(f)==s.npos){
			a2[z]=-1;
		}else{
			a2[z]=s.find(f);
		}
		}
	}
	for(int i=1;i<=z-1;i++){
		cout<<a1[i]<<endl;
	}
	cout<<a2[z];
	return 0;
}