#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("T");}else{puts("F");}
#define MAX_N 200005

int main() {
    int n;
    cin >> n;
    int a[n];
    rep(i,n) cin >> a[i];
    int flag = 0;
    rep(i,n){
        if(i == 0){
            if(a[i] == 1 || a[i] == -1)flag = 1;
        }else{
            if(abs(a[i] - a[i-1]) != 1)flag = 0;
        }
    }
    if(flag)yn;
    return 0;
}