acm freshman season - simple and

1443: Simple and

Time limit: 2 Sec   Memory Limit: 128 MB
submit: 249   Resolution: 12
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Title Description

For a set of natural numbers, seeking each interval [a, b] value

 

Entry

Title plurality of sets of input <10 ^ 6 group

Each row two numbers a, b (0 <a, b <= 10000)

while (~ scanf ( "% d% d", & a, & b)) {} may be read automatically terminate

Export

Input and output each a natural number, and represents

Sample input

186 6907
0 2475
39 3742
127 2546
195 8529
1 485
155 4754

Sample Output

23,839,573 
3.06405 million 
7002412 
3.23433 million 
36.35727 million 
117 855 
11.2907 million

 problem solutions: a + ...... + b = ( a + b) * (b-a + 1) / 2 
code is as follows

#include<iostream>
using namespace std;
main()
{
int a,b,i,j,k;
while (cin>>a>>b)
{
j=(a+b)*(b-a+1);
k=j/2;
cout << k<<endl;
}
}