https://www.luogu.com.cn/record/36790551

#include"bits/stdc++.h"
using namespace std;
int main(){
	int k,len;
	unsigned long long x = 0;
	cin >> k;
	getchar();
	len = 0;
	char ch = getchar();
	while(ch >= '0'&&ch <= '9'){
		x *= 10;
		x += (ch - 48);
		len++;
		ch = getchar();
	}
	if(x == 0)len = 0;
	if(len < k){
		cout <<'1';
		for(int i = 1;i <= k-len;i++){
			cout << '0';
		}
		if(x != 0)cout << x;
	}
	else if(len > k){
		x+=pow(10,k);
		cout <<(long long) x;
	}
		else cout << '1' << x;
	return 0;
}