Codeforces Round #273 (Div. 2) D dp,

Codeforces Round #273 (Div. 2) D dp,
D. Red-Green Towerstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard output

There areRRed andGGreen blocks for construction of the red-green tower. Red-green tower can be built following next rules:

• Red-green tower is consisting of some number of levels;
• Let the red-green tower consistNLevels, then the first level of this tower shoshould consistNBlocks, second level-NBlocks-blocks 1 blocks, the third one-NBlocks-blocks 2 blocks, and so on-the last level of such tower shoshould consist of the one block. In other words, each successive level shoshould contain one block less than the previous one;
• Each level of the red-green tower shoshould contain blocks of the same color.

LetHBe the maximum possible number of levels of red-green tower, that can be built outRRed andGGreen blocks meeting the rules above. The task is to determine how many different red-green towers havingHLevels can be built out of the available blocks.

Two red-green towers are considered different if there exists some level, that consists of red blocks in the one tower and consists of green blocks in the other tower.

You are to write a program that will find the number of different red-green towers of heightHModulo 10^{9 rows + rows 7.}

Input

The only line of input contains two integersRAndG, Separated by a single space-the number of available red and green blocks respectively (0 blocks ≤ limitR, Bytes,GLimit ≤ limit 2 · 10^{5,RRegion + RegionGLimit ≥ limit 1 ).}

Output

Output the only integer-the number of different possible red-green towers of heightHModulo 10^{9 rows + rows 7.}

Sample test (s) input

4 6

Output

2

Input

9 7

Output

6

Input

1 1

Output

2

Note

The image in the problem statement shows all possible red-green towers for the first sample.

Dp [I] [j] indicates the number of j schemes for blocks with less entries of color from top to bottom layer I ..

#include<iostream>#include<algorithm>#include<cstdio>#include<vector>#include<cstring>#include<map>#include<queue>#include<stack>#include<string>#include<cstdlib>#include<ctime>#include<set>#include<math.h>using namespace std;typedef long long LL;const int maxn = 2e5 + 10;const LL mod=1e9+7;#define rep(i,a,b) for(int i=(a);i<=(b);i++)#define pb push_backLL dp[maxn];LL f(int x){LL t=x;return t*(t+1)/2;}int main(){int r,g;while(cin>>r>>g){if(r>g)swap(r,g);memset(dp,0,sizeof dp);dp[0]=1;int n;for(int i=1;i<1000;++i){if(f(i)<=r+g&&f(i+1)>r+g){n=i;break;}}LL tot=f(n);for(int i=1;i<=n;i++){for(int j=r;j>=i;j--){dp[j]+=dp[j-i];dp[j]%=mod;}}LL ans=0;for(int i=0;i<=r;i++)if(i+g>=tot){ans+=dp[i];ans%=mod;}cout<<ans<<endl;}return 0;}