#include <stdio.h>
#include <math.h>
struct sankaku{
double a;
double b;
double c;
};
int main(void) {
struct sankaku data = { 5 , 5 , 5 };
double p = (data.a+data.b+data.c)/2;
double x = p*(p-data.a)*(p-data.b)*(p-data.c);
return 0;
}
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