#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

struct point {
    ll x, y, stat;
    point(int x=0, int y=0, int stat=0): x(x), y(y), stat(stat) {}
    bool operator<(const point &p) const {
        return y < p.y;
    }
};

int main(void) {
    int n;
    scanf("%d", &n);
    vector<point> Neg, Other;
    for (int i = 0; i < n; ++i) {
        point p;
        char res[5];
        scanf("%lld%lld%s", &p.x, &p.y, res);
        p.stat = *res != 'N' ? *res == 'P' ? 1 : 0 : -1;
        if (p.stat < 0) Neg.push_back(p);
        else Other.push_back(p);
    }
    sort(Neg.begin(), Neg.end());
    sort(Other.begin(), Other.end());
    int other_start = 0;
    for (const auto &p: Neg) {
        while (other_start < Other.size() && Other[other_start].y <= p.y) ++other_start;
        for (int j = other_start; j < Other.size(); ++j) {
            auto &q = Other[j];
            ll dx = q.x-p.x, dy = q.y-p.y;
            if (-dy <= 2*dx && 2*dx <= dy) {
                if (q.stat > 0) {
                    printf("impossible\n");
                    return 0;
                }
                q.stat = -1;
            }
        }
    }
    vector<point> Rem;
    for (const auto &p: Other)
        if (p.stat >= 0) Rem.push_back(p);
    sort(Rem.begin(), Rem.end(), [](const point &p, const point &q) {
                                     if (2*p.x + p.y != 2*q.x + q.y)
                                         return 2*p.x + p.y > 2*q.x + q.y;
                                     return  -2*p.x + p.y > -2*q.x + q.y;
                                 });
    int ans = 0;
    point *best_seen = &Rem[0], *best_taken  = NULL;
    for (auto &p: Rem) {
        if (-2*best_seen->x + best_seen->y < -2*p.x + p.y)
            best_seen = &p;
        if (p.stat == 1 && (!best_taken || -2*best_taken->x + best_taken->y < -2*p.x + p.y)) {
            ++ans;
            best_taken = best_seen;
        }
    }
    printf("%d\n", ans);
}