#include <stdio.h>
#include <math.h>
struct sannkaku{
double a;
double b;
double c;
};
int main(void){
struct sannkaku t;
double s,S;
s=(t.a+t.b+t.c)/2;
S
= sqrt(s
*(s
-t.
a)*(s
-t.
b)*(s
-t.
c));
return 0;
}
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