#include <bits/stdc++.h>
#define FOR(i, a, b)    for (int i = a; i <= b; ++i)
#define ii              pair <int, int>
using namespace std;
const int N = 1e5 + 3, Q = 5e5 + 3;
int n, q;
ii  Qr[Q];

void init() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    //freopen("main.inp","r",stdin);
    //freopen("main.out","w",stdout);
}

void read(int &val) {
    char c; do { c = getchar(); } while (! isdigit(c));
    int res = c - '0'; while (isdigit(c = getchar())) res = 10 * res + c - '0';
    val = res;
}

vector <int> adj[N];
int stt, topo[N], vis[N];
void dfs(int u) {
    vis[u] = true;
    for (int v : adj[u])
        if (! vis[v]) dfs(v);
    topo[stt--] = u;
}

int check[N];
int Count(int u) {
    check[u] = 1;
    int ans = 1;
    for (int v : adj[u])
        if (! check[v]) ans += Count(v);
    return ans;
}

bool kt(int mid) {
    FOR(i, 1, n) adj[i].clear(), vis[i] = check[i] = 0;
    FOR(i, 1, mid) adj[ Qr[i].first ].push_back( Qr[i].second );
    stt = n;
    FOR(i, 1, n) if (! vis[i]) dfs(i);
    int mid1 = topo[n/2 + 1], dem = Count(mid1);
    if (dem != n/2 + 1) return false;

    FOR(i, 1, n) adj[i].clear(), vis[i] = check[i] = 0;
    FOR(i, 1, mid) adj[ Qr[i].second ].push_back( Qr[i].first );
    stt = n;
    FOR(i, 1, n) if (! vis[i]) dfs(i);
    int mid2 = topo[n/2 + 1]; dem = Count(mid2);
    if (dem != n/2 + 1 || mid1 != mid2) return false;

    return true;
}

void solve() {
    cin >> n >> q;
    FOR(id, 1, q) {
        int i, j; char c;
        cin >> i >> j >> c;
        if (c == '>') swap(i, j);
        Qr[id] = { ++i, ++j };
    }

    int lo = 0, hi = q;
    int res = -1;
    while (lo <= hi) {
        int mid = lo + hi >> 1;
        if (kt(mid)) res = mid, hi = mid - 1; else lo = mid + 1;
    }
    cout << res;
}

main() {
    init(); solve();
}