#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
unsigned long p,i,k,q;
int main()
{int gasit=0;
f>>p;
if(p==0)
g<<1;
else
	for(i=25;i<=1000000000&&!gasit;i+=25)
		{if(i%1220703125==0)
		    k+=17;
	 	else
			if(i%244140625==0)
				k+=16;
			else
				if(i%48828125==0)
					k+=15;
				else
					if(i%9765625==0)
						k+=14;
					else
						if(i%1953125==0)
							k+=13;
						else
							if(i%390625==0)
								k+=12;
							 else
								 if(i%78125==0)
									 k+=11;
								 else
									 if(i%15625==0)
										 k+=10;
									 else
										 if(i%3125==0)
											 k+=9;
										 else
											 if(i%625==0)
												 k+=8;
											 else
												 if(i%125==0)
													 k+=7;
												 else
													 k+=6;
        if(k==p)
			{gasit=1;g<<i;}
		else
		if(k>p)
			{k--;
			for(q=i;q>=i-25;q-=5)
				{k--;
				 if(k==p)
				 {g<<i-(i-q);gasit=1;}
				}
			}
		}
	if(!gasit)
		g<<-1;
return 0;
}