int sum = 0;
for(int i=1; i<=100; i++){
    sum += i;
}
cout << sum << endl;

int sum;
for(int i=1; i<=100; i++){
    sum += i;
}
cout << sum << endl;

int sum = 0;
int i=1;
while(i<=100){
    sum += i;
}
cout << sum << endl;

int sum = 0;
for(int i=1; i<=100; i++){
    sum = i;
}
cout << sum << endl;