#include<iostream>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstdio>
#include<string>
#include<deque>
#include<stack>
#include<queue>
#include<vector>
#include<stdio.h>
#include<map>
#include<set>
#include<string.h>
#include<time.h>
#include<stdlib.h>
#include<bitset>
using namespace std;
const int N=50005;
int n,m;
int x[N*2],tot;
int a[N],b[N],c[N];
char k[200];
int fa[N*5];
int find(int x){
	if(fa[x]==x)return x;
	return fa[x]=find(fa[x]);
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=m;i++) {
		cin>>a[i]>>b[i]>>k;
		if(k[0]=='o'){
			c[i]=1;
		}
		a[i]--;
		x[++tot]=a[i];
		x[++tot]=b[i];
	}
	sort(x+1,x+1+tot);
	tot=unique(x+1,x+1+tot)-x-1;
	for(int i=1;i<=tot*2;i++)fa[i]=i;
	for(int i=1;i<=m;i++){
		a[i]=lower_bound(x+1,x+1+tot,a[i])-x;
		b[i]=lower_bound(x+1,x+1+tot,b[i])-x;
		if(c[i]==1){
			if(find(a[i])==find(b[i])){
				cout<<i-1;
				return 0;
			}
			fa[find(a[i])]=find(b[i]+tot);
			fa[find(b[i]+tot)]=find(a[i]);
		} else{
			if(find(a[i]+tot)==find(b[i])){
				cout<<i-1;
				return 0;
			} 
			fa[find(a[i])]=find(b[i]);
			fa[find(a[i]+tot)]=find(b[i]+tot);
		}
	}
	cout<<m;
	
	return 0;
}