C :

#include<stdio.h>
#include<math.h>

int main()
{
    double N;
	scanf("%lf",&N);
	if (N<0||N>100)
	{
	    printf("Fora de intervalo");
	}
	else if (N>=0&&N<=25)
	{
	    printf("Intervalo [0,25]");
	}
	else if (N>25&&N<=50)
	{
	    printf("Intervalo (25,50]");
	}
	else if (N>50&&N<=75)
	{
	    printf("Intervalo (50,75]");
	}
	else if (N>75&&N<=100)
	{
	    printf("Intervalo (75,100]");
	}

    return 0;
}

C++ :

#include<iostream>

using namespace std;

int main()
{
     long double x;

    cin>>x;
    
    if(x>=0&&x<=25) cout<< "Intervalo [0,25]" <<endl;
    
    else if(x>25&&x<=50) cout<< "Intervalo (25,50]" <<endl;
    
    else if(x>50&&x<=75) cout<< "Intervalo (50,75]" <<endl;
    
    else if(x>75&&x<=100) cout<< "Intervalo (75,100]" <<endl;
    
    else cout<< "Fora de intervalo" <<endl;
    
    return 0;
}