.

.

float fun(int n)
{
float i;
int j;
float y=0.0;
for(i=1;i<=n;i++)
{
j=i;
if(j%2==0)
y=1.0*(y-1/(i*(i+1)));
else
y=1.0*(y+1/(i*(i+1)));
};
return y;
}