#include <stdio.h>
 
int a(int n){
     int a,i;
     a=0;
     for(i=0;i<n;i++)
     {
     	a=2*a+3;
     }
 
     return a;
}
 
int main(void) {
	int n=2,result;
	result=a(n);
 
}
 
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