#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	float a;
	cin>>n;
	a=(n-2)*180;
	printf("%.1f",a);
	
	return 0;
}
/**************************************************************
	Problem: 1317
	User: chenyaohuo
	Language: C++
	Result: Wrong Answer
****************************************************************/