Recursion Grid

#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long int
#define ld long double
#define pb push_back
#define p_b pop_back
#define si stack<int>
#define sll stack<ll>
#define sc stack<char>
#define vi vector<int>
#define vll vector<ll>
#define mii map<int, int>
#define msi map<string, int>
#define mci map<char, int>
#define qc queue<char>
#define qi queue<int>
#define qll queue<ll>
using namespace std;

ll grid(int n, int m, vector<vector<int>>& dp){
    if(n == 1 || m == 1){
        return 1;
    } else if(dp[n-1][m-1] != -1){
        return dp[n-1][m-1];
    } else{
        dp[n-1][m-1] = grid(n-1, m, dp)+grid(n, m-1, dp);
        return dp[n-1][m-1];
    }
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m;
    cin >> n >> m;
    vector<vector<int>> dp;
    for(int i = 0; i < n; i++){
        vector<int> p;
        for(int j = 0; j < m; j++){
            p.pb(-1);
        }
        dp.pb(p);
    }
    cout << grid(n, m, dp);
    return 0;
}