#include <bits/stdc++.h> #define int long long using namespace std; const int mod = 1e6 + 7; const int LOG = 20; const int maxn = 1e5 + 5; int dp[2][10005][2]; signed main() { int n; cin >> n; vector<int> v(n+1); for(int i=1; i<=n; i++) cin >> v[i]; dp[0][1][0] = 1; for(int a=1; a<n; a++) { for(int b=1; b<=a; b++) { for(int c=0; c<2; c++) { if(c) { dp[1][b][1] = (dp[1][b][1] + b * dp[0][b][1]) % mod; dp[1][b+1][1] = (dp[1][b+1][1] + dp[0][b][1]) % mod; continue; } int mx = min(b+1, v[a+1]); if(v[a+1] <= b) dp[1][b][0] = (dp[1][b][0] + dp[0][b][0]) % mod; if(v[a+1] == b + 1) dp[1][b+1][0] = (dp[1][b+1][0] + dp[0][b][0]) % mod; if(v[a+1] <= b) dp[1][b][1] = (dp[1][b][1] + (v[a+1] - 1) * dp[0][b][0]) % mod; if(v[a+1] == b + 1) dp[1][b][1] = (dp[1][b][1] + b * dp[0][b][0]) % mod; if(v[a+1] > b + 1) { dp[1][b][1] = (dp[1][b][1] + b * dp[0][b][0]) % mod; dp[1][b+1][1] = (dp[1][b+1][1] + dp[0][b][0]) % mod; } } } for(int b=1; b<=n; b++) { for(int c=0; c<2; c++) { dp[0][b][c] = dp[1][b][c]; dp[1][b][c] = 0; } } } long long ans = 0; for(int i=1; i<=n; i++) ans = (ans + dp[0][i][1]) % mod; cout << (ans + 1) % mod << '\n'; return 0; }

teams.cpp: In function 'int main()':
teams.cpp:28:21: warning: unused variable 'mx' [-Wunused-variable]
   28 |                 int mx = min(b+1, v[a+1]);
      |                     ^~