Error expected primary-expression before 'if'

I am just a student and beginning to learn C programming, so I am not really on an advanced level.

I have this piece of code, and I guess that it is pretty easy to understand what I am trying to do. However I get an error saying an error before if.

I suspect that the problem is my if-else statement in between the if and else. How would you guys solve it?

#include <stdio.h>
#include <iostream>
int main ()
{
int N;
scanf("%i",&N);
if (N > 50)
        (if (N > 75)
            N = N - 25;
            N = N - 10;
        )
else
        N = N + 10;
printf("%i",N);
}