#pragma GCC optimize("Ofast") #include<stdio.h> #include<algorithm> using namespace std; long long dp[2][10005]={0},num[10005],pre[10005]={0},mod=1000007; int main(){ long long i,j,n; scanf("%lld",&n); for(i=1;i<=n;i++) scanf("%lld",&num[i]); pre[1]=num[1]; for(i=2;i<=n;i++) pre[i]=max(pre[i-1],num[i]); long long cur=0,ans=num[n]; for(i=1;i<=n;i++) dp[cur][i]=i+1; for(i=n-1;i>=1;i--){ if(pre[i-1]>=num[i]-1) ans=(ans+dp[cur][pre[i-1]]*(num[i]-1))%mod; else{ ans=(ans+dp[cur][pre[i-1]]*pre[i-1])%mod; for(j=pre[i-1]+1;j<num[i];j++) ans+=dp[cur][j]; ans%=mod; } //for(j=1;j<num[i];j++) // ans=(ans+dp[cur][max(pre[i-1],j)])%mod; cur^=1; for(j=1;j<=n;j++) dp[cur][j]=(dp[cur^1][j]*j+dp[cur^1][j+1])%mod; } printf("%lld\n",ans); }

teams.cpp: In function 'int main()':
teams.cpp:8:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    8 |  scanf("%lld",&n);
      |  ~~~~~^~~~~~~~~~~
teams.cpp:10:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   10 |   scanf("%lld",&num[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~