"If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000."

This is in c++, I ran it on ideone.com and the output was 24 regardless of whether the loop was set to while((t<6)&&(f<6)) or while((t<10)&&(f<10)).

#include <iostream>

using namespace std;

int main() {

int t=0, f=5, s=5;

while((t<6)&&(f<6)){

if(t==f){

f += 5;

s += f;

}

if(t<f){

t += 3;

s += t;

}

if(f<t){

f += 5;

s += f;

}

}

cout<<s;

return 0;

}

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