#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
float f(float d,float y,float m,float e);
float a,b,c,d,S;
scanf("%f%f%f%f",&a
,&b
,&c
,&d
); S=f(a,b,c,d);
return 0;
}
float f(float d,float y,float m,float e){
return (pow(e
,(-d
*y
)))/(d
*(4*d
*y
+m
)); }
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