#include<bits/stdc++.h>
using namespace std;
struct node{
	int l,r,t;
}ed[200001];
int fa[200001],n,m,b[200001],l;
int find(int x){
	return fa[x]==x?x:fa[x]=find(fa[x]);
}
void merge(int x,int y){
	int x1=find(x);
	int x2=find(y);
	if(x1!=x2) fa[x1]=x2;
}
int main(){
	freopen("parity.in","r",stdin);
	freopen("parity.out","w",stdout);
	cin>>n>>m;
	string s;
	for(int i=1; i<=m; i++) {
		cin>>ed[i].l>>ed[i].r>>s;
		ed[i].l--;
		if(s[0]=='o') ed[i].t=1;
		else ed[i].t=0;
		b[++l]=ed[i].l;
		b[++l]=ed[i].r;
	}
	sort(b+1,b+l+1);
	l=unique(b+1,b+l+1)-b-1;
	for(int i=1;i<=l*2;i++) fa[i]=i;
	for(int i=1; i<=m; i++) {
		ed[i].l=lower_bound(b+1,b+l+1,ed[i].l)-b;
		ed[i].r=lower_bound(b+1,b+l+1,ed[i].r)-b;
		if(ed[i].t==0){
			if(find(ed[i].l)==find(ed[i].r+l)){
				cout<<i-1;
				return 0;
			}
			else{
				merge(ed[i].l,ed[i].r);
				merge(ed[i].l+l,ed[i].r+l);
			}
		}
		else{
			if(find(ed[i].l)==find(ed[i].r)){
				cout<<i-1;
				return 0;
			}
			else{
				merge(ed[i].l,ed[i].r+l);
				merge(ed[i].l+l,ed[i].r);
			}
		}
	}
	cout<<m;
	return 0;
}