#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int n,m,x,y,d[N];
bool vis[N],ins[N];
vector<int>g[N];
queue<int>q;
void dfs(int x){
	vis[x]=ins[x]=1;
	for(int y:g[x]) if(!ins[y]){
		d[y]++;
		if(!vis[y]) dfs(y);
	}
	ins[x]=0;
}
int query(int x,int y){
	printf("? %d %d\n",x,y),fflush(stdout);
	return scanf("%d",&x),x;
}
signed main(){
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++)
		scanf("%d%d",&x,&y),g[x].push_back(y);
	for(int i=1;i<=n;i++) if(!vis[i]) dfs(i);
	for(int i=1;i<=n;i++) if(!d[i]) q.push(i);
	while(q.size()>1){
		x=q.front(),q.pop(),y=q.front(),q.pop();
		if(!query(x,y)) swap(x,y);
		for(int i:g[y]) if(!--d[i]) q.push(i);
		q.push(x);
	}
	printf("! %d",q.front());
	return 0;
}