C :

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
int main()
{
   // freopen("in","r",stdin);
   // freopen("out","w",stdout);

    int x;
	double y;
    while(scanf("%d", &x)!=EOF)
    {
	if (x > 0)
	{
		y = exp(-x);
	}
	else if (x == 0)
	{
		y = 1;
	}
	else
	{
		y = -exp(x);
	}
	printf("%lf\n", y);


    }
  return 0;
}

C++ :

#include<stdio.h>
#include<math.h>
int main()
{
	int x;
	float y;
	while(scanf("%d",&x)!=EOF)
	{
		if((x>=-50)&&(x<0))
		{
			y = -exp(x);
		}
		if((x<=50)&&(x>0))
		{
			y = exp(-x);
		}
		if(x == 0)
		{
			y = 1;
		}
		printf("%.6f\n",y);
	}
    return 0;
}