用的字符串

#include<bits/stdc++.h>
#define N 202000
#define M 2020
#define ll long long
using namespace std;
string s;
bool flag = 0;
int main(){
	cin.tie(0);cout.tie(0);
	cin >> s;
	if ( s[0] == '0' ){
		cout << 0;
		return 0;
	}
	if ( s[0] == '-' ){
		cout << '-';
		flag = 1;
	}
	int i = s.size() - 1;
	if ( flag == 1 ){
		i--;
	}
	for ( ; i >= 0; i-- ){
		if ( s[i] != '0' && s[i] != '-' ){
			cout << s[i];
		}
	}
	return 0;
}