#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
int n,m,i,o;
char f[50];
int main()
{
	freopen("wheel.in","r",stdin);
	freopen("wheel.out","w",stdout);
	while (scanf("%d%d\n",&n,&m)!=EOF){
		char ch;
		int x;
		bool flag=true;
		memset(f,0,sizeof(f));
		int o=0;
		for (i=1;i<=m;i++){
			scanf("%d %c\n",&x,&ch);
			x=x%n;
			o+=x;
			o%=n;
			if (f[o]==0){
				f[o]=ch;
			}else if (f[o]!=ch && flag){
				printf("!\n");
				flag=false;
			}
		}
		if (flag){
		for (i=o;i>=0;i--)
		{
			if (f[i]!=0)
			printf("%c",f[i]);else printf("?");
		}
		for (i=n-1;i>o;i--)
		{
			if (f[i]!=0)
			printf("%c",f[i]);else printf("?");
		}
		printf("\n");
		}
	}
	return 0;
}