C/C++ - Problema in c

#include <stdio.h>
#include <iostream>
#include <math.h>

int main(){
    int sn,n,delta;
    
    printf("Inserisci S(n)\n");
    scanf("%d",sn);
    
    delta=sqrt(1-4*(-2*sn));
    n=-1+delta;
    
    printf("%d",n);
    system("PAUSE");    
}

scanf("%d",sn); 

scanf("%d", &sn);