#include typedef long long LL; #define mod 1000000007 LL pow(LL a, LL b) { LL s = 1; while(b) { if(b&1) s = (s * a) % mod; a = (a*a) % mod; b >>= 1; } return s; } LL f[200005],inv[200005]; void init() { f[0]=f[1]=inv[0]=inv[1]=1; for(LL i=2;i<=200000;++i){ f[i]=f[i-1]*i%mod; inv[i]=pow(f[i],mod-2); } } LL C(int n,int m) { if(m>n||m<0) return 0; return f[n]*inv[m]%mod*inv[n-m]%mod; } LL n,m; LL cal(int x) { LL ans=0; for(LL i=0,s=x;i