#include<cstdio>

long long getNumber(long long l,long long r,long long mod,long long left){
    if(l%mod<=left) l = l-l%mod+left;
    else l = l-l%mod-left+mod;
    if(l>r) return 0;
    else return (r-l+mod)/mod;
}

int main(){
    long long v,t,p;
    scanf("%lld%lld%lld",&v,&t,&p);
    long long l = 1, r = 5e18+7;
    long long res = -1;
    while(l<=r){
        long long m = (l+r)/2;
        if(m-getNumber(1,m,t,1)>=(p+1)*v){
            res = m;
            r = m-1;
        }
        else l = m+1;
    }
    printf("%lld\n",res);
    return 0;
}