Since the result can be large, return it modulo 10⁹ + 7.
Code
#include <bits/stdc++.h>
using namespace std;

#define ll long long
const int mod = 1000000007;

// Function to evaluate the number of ways to parenthesize the expression to get True or False
int f(int i, int j, int isTrue, string &exp) {
    // Base case 1: If i > j, it's an invalid expression, return 0.
    if (i > j) return 0;
    
    // Base case 2: If i and j are the same, evaluate the single character.
    if (i == j) {
        if (isTrue == 1) return exp[i] == 'T' ? 1 : 0;
        else return exp[i] == 'F' ? 1 : 0;
    }
    
    ll ways = 0;
    
    // Iterate through the expression to divide it into left and right subexpressions
    for (int ind = i + 1; ind <= j - 1; ind += 2) {
        // Recursively calculate the number of ways to make the left and right subexpressions true or false
        ll lT = f(i, ind - 1, 1, exp);  // Number of ways to make the left expression true.
        ll lF = f(i, ind - 1, 0, exp);  // Number of ways to make the left expression false.
        ll rT = f(ind + 1, j, 1, exp);  // Number of ways to make the right