Help distinguish the difference

1 
#include <iostream>
using namespace std;

float tong(int a){
float tong1 = 0;
for (int i = 1;i<=a;i++)
    tong1+=i;
return tong1;

}
float luythua(int a,int b){
float lt = 1;
for (int i = 1;i<=b;i++)
    lt *= a;
return lt;

}
float gt(int a){
float gt1 = 1;
for (int i = 1;i<=a;i++)
    gt1*=i;
return gt1;


}




int main(){
freopen("tonghop.inp","r",stdin);
freopen("tonghop.out","w",stdout);
int x,n;
cin >>x >>n;

float s1 = 0;
float s2 = 0;
float s3 = 0;
float s4 = 0;
float s5 = 0;
for (int i = 1;i<=n;i++)
    s1 += 1/tong(i);
printf("%.2f\n",s1);
for (int i = 1;i<=n;i++)
    s2 += luythua(i,i);
printf("%.1f\n",s2);
for (int i =1;i<=n;i++)
    s3 += luythua(x,i)/tong(i);
    printf("%.1f\n",s3);
for (int i = 1;i<=n;i++)
    s4 += luythua(x,i)/gt(i);
    printf("%.1f\n",s4);
for (int i = 0;i<=n;i++)
    s5 += luythua(x,2*i+1)/gt(2*i+1);
printf("%.1f",s5);




return 0;



}


#include <iostream>
using namespace std;

float tong(int a){
float tong1 = 0;
for (int i = 1;i<=a;i++)
    tong1+=i;
return tong1;

}
float luythua(int a,int b){
float lt = 1;
for (int i = 1;i<=b;i++)
    lt *= a;
return lt;

}
float gt(int a){
float gt1 = 1;
for (int i = 1;i<=a;i++)
    gt1*=i;
return gt1;


}




int main(){
freopen("tonghop.inp","r",stdin);
freopen("tonghop.out","w",stdout);
int x,n;
cin >>x >>n;

float s1 = 0;
float s2 = 0;
float s3 = 0;
float s4 = 0;
float s5 = 0;
for (int i = 1;i<=n;i++)
    s1 += 1/tong(i);

for (int i = 1;i<=n;i++)
    s2 += luythua(i,i);

for (int i =1;i<=n;i++)
    s3 += luythua(x,i)/tong(i);
    
for (int i = 1;i<=n;i++)
    s4 += luythua(x,i)/gt(i);
    
for (int i = 0;i<=n;i++)
    s5 += luythua(x,2*i+1)/gt(2*i+1);


printf("%.2f\n",s1);
printf("%.1f\n",s2);
printf("%.1f\n",s3);
printf("%.1f\n",s4);
printf("%.1f",s5);
return 0;



}

Test the file .inp with the number of 8 and 9. They will display different results.
Please explain this to me.